Diet pills 5 weeks pp

I'm 5 weeks pp and I want to start exercising. When I was engaged I wanted to get in shape so my wedding dress would look prettier on me. So I started taking some diet pills which they worked perfectly. I got married, got pregnant and now I want to take them again. Is it ok to be only 5weeks pp and take them? Should I wait? I don't want to ask my doctor since I know he will tell me I shouldn't take them at all, help please!