Sharp Lower Abdominal Pain and Irregular mensturation

Hi,

So for about the last six months, maybe a bit less I've been getting my period every 10-14 days instead of every 28. Sometimes its light and not painful, other times its extremely heavy and I have cramps so bad I have to take 5 Tylenol twice a day. Either way it lasts 5 Days almost on the nose.
With this, I get a sharp pain on my lowe left abdomin, just above my pubic bone. Usually when I get the sharp pain I also have a bit of swelling, it looks kind of like a golf ball being pressed up.

Does anyone know what this could be?