We don't have sex than often since my son born!! :(

Since my son born 2 1/2 yrs ago my husband I I don't have sex that often.. I am talking about every 4 or 5 months.. Last time was 1 month ago.. I roll him that we need to do something about it.. And he said it will happen and never happen.. I feel weird because I gain weight and in the process to lose it... And feel like he don't like the way I look :(... Well I don't know... And personally I will love to have SEX everyday day...!!!  What can I do.. Sometimes I feel guilty because I remember my old times with my ex boyfriend   that he was very sexually and we was doing it all the time and it was so damn good!!!