Not enough sex!!

My husband and I we've been together for 11 years. We have a good relationship in everything except our sex life. When we have sex it's great it's amazing he satisfies me no complaints about his performance in bed. The problem is we don't have enough of it he says he finds me attractive sometimes and sometimes he doesn't. The worst feeling in the world is feeling unwanted, and that's how I feel. He will just have sex with me when he feels like it we literally go more than 20 days 10 days without touching eachother and it was not like this in the beginning. We couldn't keep our hands off eachother. Then little by little it just died out. I'm really frustrated because it makes me feel like I'm not good enough or that there's more I can do but to tell you the truth I'm tired of having the same argument with him about this subject. I'm not begging for sex and I'm not gonna be that desperate needy wife, but I'm tired of arguing with him then ignoring the problem and then argue about it again. Anyway just needed to vent and any advice or tips would be helpful I've tried everything to spice it up but I can't help it if he's attracted to me when he feels like it. So annoying!!!