4 months after baby, getting my belly back?

4 months ago, I had my baby.. and I know that it's gonna take a while to get my belly back.. but I need some help! I can't really do crunches because I have hip problems, are there any other exercises I can try? Also Ive been dieting and it's been working somewhat but I'm willing to step it up a little.. any suggestions? I just want my little belly back :( Also, it seems like a wrinkly mess.. what can i do for this?