I have developed a bump on the back of my head, at the base of my skull on my right side. I noticed it this morning while washing my hair. It is a little tender to the touch. It is about the size of a quarter. I am currently on lamictal and keppra for grand mal seizures. Should I contact the dr.? I haven't had any trauma to the head, so don't know what could be causing this. Any help is appreciated.