Sounds like you have MRSA
It sounds like the spot on the base of your spine was a pilonidal cyst. Because you said it spread some, check out a dermatology website about hidradenitis suppurativa. I had to eventually have the cyst and the 'sack' removed from my tailbone and have had several more crop up - some on the insides of my thighs - and a couple under my breasts. Hope this helps. If anything crops up again, I find that warm compresses help to take the soreness out - and even using hot compresses can help bring them to a head and help them drain. I still end up at the docs getting antibiotics most of the time. I have been known to carry fever with mine as well.
Good Luck.
my 4 year old daughter has these bumps all on the inside of her thighs and creases in her knees..... the doctor told me it was a virus and started with an "m" i wanted to do more research on this but i cant remember what it was called. he said the only cure is to freeze them off
my son has the same thing! the doctor said it would go away on it's own but never did! it is spreading now!!!