Confused/angry

My husband and inhave been together 8 years and have 3 boys together. We have had our fair share of problems and i am partially to blame for some of them but we are in an area right now where i dont even know what to do. Ive gained a significant amount of weight with each child and ive tried to diet/work out but nothing has happened and about a year and a half ago.i was diagnosed with PCOS which makes it hard to drop weight.

Back in July my husbands High School girlfriend came to town and we got into a fight about her and going out to dinner (as a group with her) because of an incdent that happened in February (he texted her saying i love you and she said it back and they both said it was just as friends). Well long story short he cheated on me with her lied about it and then spent almost 2 days telling me he might want to be with her instead. We decided to try and work itnout we do have 3 kids and im still in college (went back after being out for years).

Jump to this last week we have a big no porn rule because ive been open to havung sex whenever he needs me and it just goes against some of our values and he was caught watching porn. I told him i don't feel like im good enough for him and obviously he isnt attracted to me because he needs more than me to keep him sexually happy. On top of that I offered to have sex with him yesterday (his birthday) he turned me down, offered tonight and turned me down again. It seriously is making me hate myself and the way i look way more than i already do and I just don't know what to do anymore.

Any advice, kind words or anything would be greatly appreciated.