I am a 17yo healthy male. I'm sexually active. No std's, tested. It's almost every day or every other day that my girlfriend and I are sexually active. About last week I got a lump on the right side of my penis, it only hurts if I poke it or put pressure. It lasted two days, first day it was bigger than the next, but after three days it was gone. It appeared again yesterday, right after my girlfriend gave me fellatio services, same as last time. Should I be worried?

Yes, I would go and get tested again and let the doctor exam it.