need advice >.<

So I have this disease that causes my hormones to change a lot and that includes my sex drive, when my boyfriend always wants to do stuff and don't get me wrong he is hot and attractive but I'm always " not in the mood " I can't really force my body to be turned on and my sex drive is really low most of the time, and I feel like I'm letting him down a lot, is there any ideas on how to maybe work this out so I can make him happy?