Overweight concerns

What concerns have you faced so far being overweight? I am only 4 weeks but I am 300lbs and I am hating myself because this is the highest I've ever been and after trying for over three years it happens now... I want to give my baby the best chance I can. I'm cutting out junk food and cooking at home. Last time I did that I lost 40lbs. I'm still very nervous! My sister had my niece six months ago and had a variety of issues :(