my wife keeps begging for sex but I'm disgusted by her and cheating?

[burger]

we have got 2 children who are 5 and 3 years old. We have been married 5 years now. She's 30 and saggy and old. It was her birthday yesterday and I forgot about it. She got really mad and wanted me to make love but I couldn't because she's saggy and out of shape. She had the kids then lost weight and now she has gained over 10 pounds. I'm not attracted to her and I have cheated and had affairs she knows about. She found out and asked me why, then I said because she's not attractive. She said she would start working out and caring more about her looks but I haven't seen a change. She wants another baby and I wouldn't mind but I can't get it up for her