Bleeding while having sex

So me and my boyfriend have been in a relationship for a year and a month , and at the three month point we started having sex (fingering me, eating me out) btw he is a female to male transgender so that's all we can do. But anyway, recently when we have sex every single time i start to bleed every where, and get a huge rash on my vagina. And i get so embarrassed and grossed out by myself, he reassures me and tells me he still finds me perfect but i'm scared there's something wrong. He's not scratching me bc he barley has nails and i would feel it, and it happens when i masturbate too. My body is small, i'm 5'5 and 106 but he's not big either he's 5'2 and 140. So his fingers aren't big in the slightest so i don't think he's stretching me out and my cherry popped years ago because i was masturbating. Any advice on what i should do?