I've felt exactly as you have. My DD is nearly 7 and since she was born I've never really felt like sex. There is usually a gap of around 4/5 months between times. I do it then because I tell myself, if I do it once, I'll realise I like it and want to do it more. Or I just get really drunk. I do find I enjoy it once I am in the zone, but it will be another few months before it happens again.
What I have come to realise is that there is an underlying problem in my marriage. I don't respect my DH particularly, although he is a decent person and a good father. He spoils me on special occasions and is in no way violent or abusive. But he takes me for granted a lot, is not able to support me emotionally (ever) and is something of a doormat. Ultimately we need to work on our relationship and we've started that now.
What did I do to get my mojo back? I had an emotional affair. I'm not recommending this as an option, just telling you what worked for me. I met someone who was all the things I would look for in a man if I were in the position of looking again - confident, smart, witty, funny, doesn't take any crap. Every time we had a 'sexting' evening my DH got lucky - there was no other outlet for my sexual energy. The affair lasted about 4 weeks and in that time me and DH had more sex than we'd had in the last few years. He doesn't know why things have changed, but now I'm back in the mood were keeping up the frequency. I'm hoping this will help us rebuild our relationship, although would give us 50/50 at the moment of still being together in a year.
For me, I came to realise I did have a sex drive, I just wanted it with someone else. The affair is over, I have my sex drive back, now I just need to decide if my marriage can be saved.