Hooking up with my best friend ... anyone?

I’ve been hooking up with my best friend for over a year. We dated for a hot minute. We had a miscarriage in October and we lived together for a few months last year. I found out he’s had a long distance gf. I messaged her anonymously. I feel bad. I just didn’t know. I would never choose to be that other girl. I hate this so much. I think she deserves to know. He’s helping me with the miscarriage bills and I don’t want to get on his bad side. I chickened out I don’t know how to tell her so she believes me without throwing myself under the bus and not getting the help with the bills that are rightfully both of ours. I hate this all so much. Please no negative comments, I had no idea and I’ve gone through so much with this miscarriage and he has not been supportive at all and I just don’t know what to do. I need some advice. If these were my only medical bills I would just say fuck it, but I also was in a terrible accident last year. Ugh.