black/purple/red lesions

I am 23 years old and have seen two doctors for a recent development of a skin condition.  Never in my life have I had acne, much less whatever has taken over my jawline and chin recently.  The two doctors I have seen ran no blood tests and put me on an antibiotic (dioxcycln), twice a day for a month.
symptoms:
black and purple lesions that are symmetrical to each other on either side of my chin, concentrating near the jawline and working their way up to the mouth.  If touched, the black and purple seems to concentrate for a minute, turn darker, and then spread further underneath my skin.  Initially, the lesions started off as little red bumps, soon swelling so large that my skin burst open throughout the night expelling brown and yellow cream/pus with a large amount of blood all over.  A few of the lesions look like spider bites - with a hard white center that will fall off and be replaced by yet another hard white center.  The lesions are on average a few mm, but the two largest ones are each nearly an inch across.  The lesions are accompanied with extreme itching and excruciating pain.  It has spread to my thigh.

Please help me.  I feel like the doctors (not dermatologists) just rushed through and diagnosed it as a typical skin infection.  I am not having much of a response to the antibiotics.