If you can I would seriously try to change your boyfriends mind about the dog. I inherited a cat from my husband’s ex and resented it for years. Now about 5 years later I am ok with it, but I would rather not have had to deal with it and hear it whine all the time and be reminded of BM neglecting her responsibilities and me picking up her slack every time I had to feed the cat or change the cat litter. If your boyfriend insists about the dog then I would tell him that he has to do everything for this dog. He has to walk it, feed it, train it, clean up after it, take it to the vets and pay for everything to do with it and that you will not be doing any of those things. And STICK TO IT. Trust me, I failed when I started to be the main caregiver for our cat, now it is my “job” to do these things most of the time. If he can’t be home to walk the dog, he can pay for a dog walker. If he can’t afford the dog, then he should not be taking it on. 

As for comparing the girls it will be a struggle not to with them being so close in age but they are different individuals and will have different personalities and abilities. Reframe your daughters behavior as her asserting her independence and showing leadership qualities. Help show her how to keep those traits but also to be more polite and respectful while maintaining her assertiveness.  reframe her behavior as possitives that need refining. 

She is a future leader in the making, use words that empathize her attributes as positives: 

https://hbr.org/2018/05/the-different-words-we-use-to-describe-male-and-...

If sd is throwing her prosperity at her mother’s in your children’s face then that needs addressing. Work with your boyfriend (and maybe BM if she might be willing) to address that with sd. I would develop a sentence that shuts that kind of talk down along with discussing with both girls how different people and different homes have different things and that is ok, but not something that we should boast about if we come across those that have less than us. Equally they can learn to be happy for someone who has more than us even if we know that we will never get what they have. These are difficult concepts to embrace for young kids who naturally want to boast about things but not one that should be avoided. 

The phrase I use in our house (which is much better off than bm’s house, but we’re not millionaires either) is that there will always be people with more than us and always be people with less than us. 

The girls are 3 years old.  There's no way your SD is throwing anything in your daughter's face.

Your SD is the only child in her mom's home.  She has 2 adult siblings.  As a result of that she WILL have more stuff and more experiences than your kids have.  She will be able to take part in things that your daughter will miss out on.   Once they start going to school, your daughter (and their classmates)will notice the material differences/opportunities between her and her sister.

That’s what I said, 3 kids one of which is not born yet. Nothing wrong with having more kids but you are complaining  about their behavior compare to SD and inability to provide as much as BM does so maybe it’s becoming too many to handle 

and since you see a therapist I’d discuss your choices in men. This is a man #2 in your life who is useless and you have kids with both. It’s important to discuss roots of your problems. 

if BM is older and already raised children, she likely is more experienced in parenting and knows some amd that’s why her kid behaves better. She is older and likely makes more than you. Since her other kids are out of the house and don’t need monetary help as much she can spend it in SD. You said you work in day care. It’s typically a low paid job. I’d never be able to support anyone with that money.  If you like working with children, perhaps you could become certified teacher, or since you were a CNA (another low paid job), you can become RN, it will be more stable. You can take your classes in the evenings. I only ever went to school in the evevjng pr weekend because I worked during the day. In order to do that I recommend as I said before to not have  more kids at the moment. Get your life in a better shape and then have more kids. You have no control over what others fI in their home. But you have control over your own household 

If your outlook on materiastuc things is different than BMs, then what do you care what BM does. Teach your DD your values if you don’t care about materiastuc stuff 

She is 3. How is she throwing it at your DD all the time? Is she a genius of some sort? If you just worry about the future, it’s a waste of time. SD might grow into a classy lady and not throw anything in no one’s face 

He doesn't need to love his children more than you, he can love you all equally - though in different ways. What about the fact he doesn't do nice things for you? It sounds like you don't think you deserve to be treated as well as the children. He should, at the very least, do something nice for you once in awhile - especially since it sounds like you do more work than he does that helps the family function.

My dad was a "wonderful dad" for his generation - played with the kids, drove the car on vacation, cut the turkey, helped with discipline - but day to day care was my mother's job.  But times are different now, and him just "playing with the kids" is not enough. He needs to help you with day to day parenting tasks (homework, baths, dinner, transportation, laundry, etc).

His ex obviously wanted him back, so he should have been wiser than to sleep with her with no protection - that's on him, too.

I'm sure he does have good qualities, everyone does.  But he's not helping you out with the children he helped create.  At the very least, let him know ALL care of SD is now on him, and you expect him to help with his two with you, as well.

Your BF is an idiot and he thinks you're a fool. That's why he's feeding you that ridiculous line about birth control. 

  Your BF and BM broke up.  He started dating you.  If she was no longer having sex, why would she continue to use/need  birth control????  Why would a financially secure, empty nester, purposely get pregnant from a man that just dumped his pregnant girlfriend???  What your BF is telling doesn't make sense.

At the end if the day, many of the feelings you are feeling  come from the choices you made.  This great guy dumped you while you were pregnant. During that time he got another woman pregnant.  You made the choice to get back with him and have another child.  You're making the choice to take on his parenting responsibilities when SD is in your home.  You're making the choice to continue working in a day care center instead of taking steps to increase your earning potential.

If you want things to be better, take closer look at the life choices you are making.