I keep getting small blisters on my lower backside and on the corners of my mouth. I have also noticed a small lump underneath my skin on my lower backside. I am unsure of what this is and it is troubling me. I do not have health insurance so I can't get it checked out. Should I be worried about it. This is the third time in less than three months that it has come back again. I find that taking a hot bath and letting them soak helps them to bust and go away. It is a possibility it might me a sexually transmitted disease?