I was diagnosed with an 8mm cyst on my peneal gland back in 2002, I have severe headaches I haven't seen a doc since. What treatment is there for this?

Medical evaluation. The brain is a delicate structure encased in a ball of bone. It has little capacity to manage increases in pressure. If your cyst has grown over the years, it can be increasing pressure in the brain. One of the symptoms of increasing pressure as headaches. You can't treat this. You need to find out what's happening to this cyst. Now. If you are in my family, i'd be making an M.D. Visit for you.
See doc. Pineal gland cyst, because of its location in the brain, may lead to headaches and visual changes such as double vision, especially if cyst is enlarging. Cysts greater than 5mm are considered large. Please see doc for a repeat mri. In some cases, surgery may be necessary. One will not know if the severe headaches are related to the pineal gland cyst or not unless further evaluation is done.