if you havent had any success with doxy then i would suggest you try a different antibiotic such as minocycline or even keflex. i had bad cystic/nodular acne last year that was just awful and i was so down about it but then after trying every antibiotic out there i tried the keflex and then spiro. keflex stopped the acne in its tracks in 5 days and then spiro keeps me clear for good now. its amazing stuff and i have like no side effects except for sometimes i dont get my periods on time but thats about it. i feel great on it and only wish i did it 4 years ago when my derm suggested it. it might have stopped me from having the scarring i have now. that is what you want to avoid is because once you get scars its almost impossible to get rid of them. i know how you feel though i felt so gross in front of my husband and just cried every single day. keflex saved my life but talk to your derm and see what they say about it. sometimes they will even give you prednisone to calm everything down.
one more thing for myself when i have cystic acne bp wont touch it at all because its just too deep. aha usually does work pretty well but i think its more of a preventative thing and wont do much for the cysts you have on your face now. anyway that is just my two cents but i would go back to the derm like stat. i would either go the antibiotic/spiro route or just go right on the tane but whatever you dont wait around too long to do it.