Large bump with black scab every 2 months

[Bry47296]

Hello...I haven't had luck figuring out what these bumps are from doctors...yet.  Still in that process.  But thought I'd see if anyone here has a clue.  I get these large, slightly painful, bumps that used to show up on my torso.  It's always just one at a time, and start out looking like a normal pimple.  Then they become large, painful, and have a scab in the middle.  When they heal in a few weeks, they leave a scar.  This has been happening for a few years.  Then a few months ago, for the first time I got one on my legs.  When it healed, a month later another shows up.  Then another.  5 total on my legs.  Now the current one is on my butt.  My doctor said it was a MRSA infection, and gave me antibiotics.  Then anther one showed up, so he did a MRSA culture test, which came back negative.  I decided to see a dermatologist.  He also said it looked like MRSA...another culture test, again negative. Since that one was healing,  he said when I had another one, he would get a sample and do a biopsy.  Well I have one now, but he's out of the country until next week.  Hopefully by the time he can get a sample, it will still be there.  

Anyway, anyone have a clue?  I'd like to post a pic.  (Of the previous one on my leg...not the current one on my butt)  But every time I try to upload to my profile, it says internal error.

Sorry for the long story...just tried to get the important facts.  And thanks for any info in advance!

[Espy1313]

It's there anybody in these bumps? Could it be an ingrown hair? It a hair just coiled up under the skin?