No sex drive!

I feel like the absolute worst fiancé ever! I have absolutely no sex drive at all! We have a 20 month old who I still breastfeed. I’m a stay at home mom and I also babysit a disabled 9 month old. I feel like all I do is take care of babies and clean. I also have an eating disorder that I’m seeing a therapist for. I don’t eat much at all so I don’t get very much extra energy and whatever I do have my daughter takes while nursing. So I constantly am tired and feel like death. Before our daughter was born we had sex allll the time! 5-7 times a day anywhere and everywhere! After she was born it went down to maybe once a day durning nap time until she was around 4 months and my ppd really hit me and my eating disorder started. We still had sex pretty often couple times a week. But now I feel like I’ve completely lost my drive we have sex maybe 3 times a month. I have absolutely no desire what so ever. Anytime he even asks or mentions sex I get kind of angry at him for even thinking about it. I wish I had drive. I wish I wanted to have sex I really really do but I dont. And I don’t know what to do about it or how to help it