bump problem

so I have a small bump on the crease between my inner thigh area and pelvis. I don't think it's serious because I've only had protected sex with people who I was their first time and it's been coming and going for over a year. it will start to swell up and the. shrink after a few weeks. any ideas as to what it is or how to get rid of it? it doesn't hurt and feels like it's filled with liquid