When chemistry is lost in marriage..

My husband and I hardly have sex. Lucky if we do it once a month and the motivation behind that is to try and have a baby. Looking back I have been the main initiator in our relationship. He tends to not have that hunger for sex. Its like he is perfectly fine without it. I don't think I want to stay in a marriage like this...it feels like a prison sentence. Is this marriage doomed? I've discussed with him that I need that aggressive style sex where I feel desired and wanted. Its like its just not a part of who he is. I know he isn't gay.