I have had severe pelvic pain for 4 months now, what could be causing this?

Too many things!: Please see a dr.This can be anything and we (on a open forum like this) can only answer generally and never specifically as it pertains to you.This is problem you should not allow to persist:see someone asap for a proper dx!

Get checked..: It is difficult to tell with just your question...Specific location, timing/relation to activities etc..Walking/sleeping/during relation etc...Can help tease out cause. Infection such as pelvic infllammatory disease can certainly do so, as well as ovarian cysts, salpingitis (infection of your tubes) etc..Since it has been 4 months, i would consult doc..Likely need exam and ultrasound. Good luck.

Cyst, infection ,atr: Uterus, vagina, colon, or bladder can all cause pelvic pain, inside. Any one, two, or all could be infected, full of cysts, or thin/raw(atrophy) . Most likely need to see a doctor for thorough history and physical of these areas.