feeling worse by the day

so here it goes this is my mental health back story. i was a pretty happy kid until I was 9 and my parents told me and my two younger brothers that they were getting a divorce and I was really upset and started crying a lot and taking all my stress and anger out on my family and eventually I realized I can't do that so I started taking it out on myself self harming before I even knew that existed so I would twist my thumbs backwards and I ended up actually breaking one once and then my parents made me start seeing a therapist so then my parents realized that their arguments made me upset and decided against their divorce so now they are together and basically miserable. ok so that's when it all kind of began. but three years ago I started seeing myself as a lot larger than other girls my age when I wasn't and I knew about binging and purging so I tried it and sort of mastered it but I only did that maybe once a week for the last three years. but I started really self harming and cutting a little over two years ago and it wasn't a minor thing I would do it in the shower until I passed out from blood loss then often times keep going. I also always did it on my upper thighs so until I was in a bikini no one ever saw it. I am 306 days clean right now though. but one day I was wearing pajama shorts and my mom did and sent me back to the same therapist who is now probably my best friend. I was diagnosed with depression and severe anxiety in almost all fields but worst in social situations and in the past two years I've been on 17 different medicines and I am currently on 4. starting maybe last Friday my suicidal thoughts became a lot more prominent they never really left but I was able to go to school and do normal things without the contemplation of suicide constantly but right now that's all that's on my mind. I've had a boyfriend since March so about 6 months now and we are really close and for years before we were dating he was my best friend but then I started liking him and he admitted he'd liked me for three years as of march and here we are he is definitely not in the relationship for the physical things but we have gone fairly far in those ways (ive given him a blow job) he's the only one outside of my family and drs that knows I have depression and anxiety we were almost going to have sex once but I realized he doesn't know that I ever self harmed and obviously if he saw my upper thigh area he could tell in an instant so I said I wasn't ready and he was ok with it.. so back to eating disorder stuff. this summer it got really bad I'm 5'9 and I was 140 a perfectly healthy weight but I starved with a little bulimia and ended up losing 35 lbs so now I am 105. and my boyfriend asked me why I've gotten so bony and said that he misses my thighs and when I was more than just skin and bones and so I'm really scared to tell him about how i actually lost the weight but I hate lying to him and telling him it's a medicine that I'm on that's making me so skinny so I don't know if I should tell him or not and I am scared he will be dissapointed in me. I also have a concussion right now so my brain is really messed up and I don't know what to do because homework just make it worse but homework is a priority and my teachers don't care about my mental health. so I'm stuck and super stressed. any advice?