help! weight loss struggle

hey all. I need some help. I've been trying to lose weight for ever but I always give up. I've always been over weight. at this point in my life I want to change. I want to be healthy but in having a hard time figuring out what is best. I'm 24 married and have 3 kids. I need to be healthy for them but I want to be healthy for me. any advice you have will be appreciated! I'm 5'5" and weight 325 pounds....so yeah overweight. I'm depressed and it's hurting my marriage. I'm a stay at home mom to my 2 little ones and I do walk 40 minutes twice a day to bring my daughter to and from school.

I'm accusing my husband of cheating on me because I'm not attractive even though he says I am (he isn't cheating). thank you for any help!