Penis throbbing

Hi im 23 male and this jus started happneing about month or so ago and doesent seem to be goin away. Best i can explain what is happening is when i sit or lay down a certain way with maybe a lil tension on my penis it pulsates and throbs kinda feels like a heartbeat its been getting really annoying laying down and trying to sleep i dont feeel it much when i stand i can deffinily feel something goin on in my penis it doesent hurt and i can still get a erection no blood comes out or anything just feel it pulsating i got no medical insurance yet jus trying to see if anyone has any clue why this would just start to happen overnite and now wount go away