What Causes Recurring Itching And White Head Pimples On Genitals?

Within the last year or so the right side of me private parts have been itchy. When it 1st haplened i would scratch it, and the itching got worse. When i decided to look i saw, what looked like, big white-head pimples. I tried to pop them but couldnt, so i took a needle and poped them. What seemed like puss came out of them & washed them throughly. I put psoriasis medicine on it, cause i get bumps like this on my fingers since i was a kid and it always helped. This is the first time ever on my genitals. After i pop them, treat them, and stuff... they go away for awhile then come back in the same spot. I thought i might of had an std cause i found out that my ex - fiancé was cheating on me with every guy she met. No lie there & wasnt using protection. Then i was wondering why in the same spot everytime? If it was an std, wouldnt it be all over? Please help me understand what is going on, gettting scared