M.J.
A couple thoughts: you are not being selfish - you are being smart! It's so good (in my opinion) to think all this through now. I mean, think about all the animal shelter questions about: "are you ready to have a dog?" but no one seems to talk about doing that kind of self-evaluation about having a kid and it's, you know, kind of a bigger step!!!:)
Also: I've found that most moms (for some unknown reason)like to complain. I've never heard a conversation about: how fulfilling my time with my daughter is or how my soul is filled by her laughter but I've heard COUNTLESS conversations about stretch marks, lack of sleep, gaining weight etc. It's almost like we are bragging about how hard we have it - it's so weird. I don't know why that is. But when I think to myself: is it all worth it? I unwaveringly holler: YES!!! But that is never the way it sounds from conversations with my girlfriends - in reality, I am sure they'd all say the same we just don't talk about it that way.
Another thought: I actually ended up loving my body MORE than I did before my pregnancy! I know many women HATE everything about pregnancy and childbirth and there is unquestionably a lot of cause for that view. But for me, my body had never seemed so useful, so good at something. It was like all these random body parts were doing what they were intended for! And, I don't know, I loved seeing the amazing things my body was made to do. It certainly may not be that way for you but I also think some of it is perception. If gaining twenty pounds (or forty) ONLY means "fat" and "ugly" then that's probably how you'll feel. But if that extra weight can be a great time to allow your body to be in control of itself - you get to just get out of the way and do all it demands, knowing you will be able to perfectly return to your previous weight in just a few months...I dont know, I think you can even appreciate it.
Anyway, I feel a little "pollyanna" about this response but I just wanted to point out that some of your fears may not turn out the way you expect at all and also to add that women place a disproportionate amount of focus on the suckiness of motherhood and don't talk much about the amazingness - which IS plentiful! :)