alright, about a year ago i had a lower molar removed, it was a pretty rough extraction and i remember he had to leave half of the root system in place as it wouldnt come, anyways it healed fine (or so i thought) then about three months ago the area began hurting alot, by this point the root that had been left in had erupted through the gum surface and was like a little sharp tooth almost, i went to the dentist who said it seemed like the bottom of the remaining root was infected - she gave me some antibiotics and the pain seemed to go away for a couple of months, i then went to the hospital and recieved treatment for another condition i have which involves surpressing my immune system, my dental abcess flared up again so i went to the dentist who decided to pull the tooth, i explained i had a weak immune system so i might need antibiotics, but she told me its fine and now the root was gone the infection would be fixed

the pain then disappeared for about three weeks, when it came back again, the exact same pain, same place, it sent shooting pains to the same place on my head etc, so i can only imagine its pinching the same nerve - i went back to the dentist who perscribed me 250mg amoxacillin for 5 days, the pain remained so i returned and got 500mg amoxacillin for 7 days, however the pain is still here, i've been to the dentist like 8 times in the space of 3 months now and they constantly make me feel how im somehow being a nuisance, but this is a huge problem for me, at night the pain keeps me awake and sends shooting pains into my head, im struggling to revise for my university exams, and to top it off the hospital said they cant give me my immuno surpressants until they know the infection has gone (if i dont get my immuno surpressants, i can get very ill) now my dentist is telling me it "looks healed" because theres no physical damage to the gum and its not sensetive to touch, however she showed me just last week the infection on an xray, i dont understand what to do or what options i have right now, my dad called the dentist this morning pretty angry on my behalf and now i've been prescribed something called metronidazole which im about to start taking, however it looks pretty hardcore and i cant help but worry it will conflict with my immuno surpressants or something, a running theme throughout all of this is that my dentist hasnt really been sensetive to my personal needs and condition, im not sure if she just doesnt understand about my main hospital medication or she just doesnt care or what, i dont even understand how the infection is just meant to heal unless theres some way it can drain

what should i do??