Just can't do it, I want to, but can you help me figure out how?

Lately I am not interested in and I am just not turned on when my bf touches me. I am content with just the masturbation but I think it's because I can't seem to get turned on ually. Nothing seems to work. I don't know if it's something that I am eating or that I need to eat but something's gotta give. Seriously. I feel bad because as much as I really want to make love to him, I just can't get...ummm....lubed and I don't like the otc lubricants. What can I do