i felt that way when i first moved in with my fiance. we had several serious talks along the lines of what things were absolutely not acceptable for me to stay in the relationship. if nothing else, he needs to respect what you say in front of the sd even if he doesn't agree and then after you get behind closed doors you can discuss it. if my fiance didn't back me up in front of them, i would have left long ago and he knows it.

you don't have to lose your life/needs/wants just because you are with someone with kids. your feelings matter just as much as his and your sd's, but you have to speak up for yourself and stop being afraid of her.

i was so afraid of the kids at first, but once i relaxed and remembered that i was an adult and that the adults decide the rules for the house, i felt much better.

some things still suck, but overall i think i have it pretty good.

My DH is the same way because he only gets to see SS on the weekends and wants him to play and be a kid. For a while, SS was pulling lots of crap and getting away with it. I put my foot down because I've had it. If he can't follow some easy rules, he can deal with the consequences. I know how you feel! You live there too and have a right to have a say in your own home and it's in SD's best interests, I hope your DH will understand that. It's better if you can nip this in the bud now before it gets worse when she's older, like for me

Somedays I feel like I come in after the "dog" that they had when they were married...LOL...my DH had a weird way of handling his daughter...she does whatever she feels...you know it is not the poor childs fault that he and her mother divorced. Can you imagine...how many more years can she act like a little snot and get away with it??? I have absolutely no say in anything to do with her. My DH talks to his ex, his ex's family, whatever whenever he wants and doesn't feel like it is any of my 'business'...NICE HUH?
Now realize that we have a wonderful marriage when SD is not around and honestly I can pretend she doesn't exist. I know that sounds horrible but I went through the taking her places and being nice and bonding with her. SHe used me to get what she wanted and did whatever she wanted. Whenever I mentioned her extremely bad behavior, i got the really none of your business look...but my DH still expected me to be a wonderful SM and do things with her...HELLO???????
So my advice for you, get control of it right now, decide with your DH what your role really is, if you are just going to be the person that has to wait on Princess hand and foot when she is around, get it out on the table now. I wasn't willing to let her run my life.
We spend 0 time together as a family now. I do what I have to to keep sane which means I avoid any time with SD. She is happy spending time with Daddy alone and I go with my boys. The only one meserible in the whole situation is DH...funny huh? He can't have it both ways, now he has to deal with all her crap...
Don't get me wrong, I hate it,,,I feel like I don't have a family, I love my DH so much but I'm so afraid that we won't make it because he just won't open his eyes. Relationships are sacrafice, but everyone has to make some, in my case me and my children seemed to be the only ones trying, she didn't have to change anything???????
Good Luck....I hope you nip it in the butt before it gets out of control like my life.
PS...seriously get control before she gets older...it becomes pure hell then