Need some advice to get me started

I'm new to losing weight. I've always been big my whole life and I want to just get rid of it so I can be the mother my son deserves, be hot for my husband and for myself, and just to be healthy overall! I get crazy neurotic about my diet... I never know what I should or should not be eating (other than junk food, I know I shouldn't eat that LOL) and I never know how much... so I always end up barely eating at all, or way overdoing it... Anyone have any advice as to how to get started and what I should do to get a better handle on my diet?