Advice pleaseeee

I've been having random bleeding at random times of the month when I'm not due and always get a lot of stomach cramps like below my tummy but on the sides of my v line. I've also gained a lot of weight recently and my boobs have been extremely swore. I don't really know why this has happened so randomly because before now this hasn't ever happened. I'm on my period now so obviously not pregnant but I can't use tampons and more cause a bit swore down there. Just dunno what to do really, do I go doctors? Or does it just take a few years for side effects to kick in? Xx