I have a big white bump in my head it's been here for over 6 months and still has not popped by itself it doesn't hurt but what could it be?

Sebaceous cyst: It is probably a small cyst, also called a "wen", which is common on the scalp. The oil glands in the scalp get blocked with dead skin, and the oil/skin builds up under the skin to form the cyst. Nothing has to be done if they don't bother you. Sometimes they can get infected, then you have to see a dr. They can get quite large at times, and need to be drained. This can be done in the dr office.