[miss firing]

I've been with my boyfriend for over 3 years now and I love him to bits but we've been having sexual problems for well over a year. The longest time we've been without sex is 6 months. I really want this to work but it just seems that everything we try to put the "spice" back just doesn't work. I'm not 100% sure I even fancy him at the moment but i do want to. He assures me that he still finds me attractive but I know I have confidence issues myself. I hate making him feel rejected but don't want to just "put out"- where's the integrity in that? I don't want to make the biggest mistake of my life and either get married when its not going to work, or finish it, if it can get better. I feel like he's my soulmate and I really don't want to lose him- anyone got some advice for me?