Huge clot just came out

So I've been complaining to the doctors for months about my belly pain. Every month I get the same agonising pain 2 weeks before my period all the way up until my period comes. The pain is so severe I puke sometimes and I cry of pain. It keeps me awake through the night. They've passed it off as "PMS". Then I have severe heavy bleeding, like have to change my tampon every 20/ 30 minutes and it's dripping out.

Also when I go to empty my bowels it kills and there's also blood when I wipe. Just now I came out the bath and changed my tampon, 30 minutes later I feel it leaking so I go to change it and I just seen a huge clot come out? Is this normal? I'm due to call a doctor again but l'm out of town so have to wait until Monday when I'm back. But does anyone know what this is or if it's just PMS?