please help.

The past couple months my period has been off. It's been super light and occasional spotting in between periods. I thought maybe because the periods were light I might be pregnant, however, every home test take was negative. Yesterday I started my period for this month. I felt abnormal cramps and My period was heavy. Today I had a large blood clot I didn't inspect it too much but I could feel it, it was the size of a golf ball almost. I've had a few more larger sized blood clots not as big as that first one but a little larger than normal. Has anyone else experienced this? Anyone possibly able to give me some help or advice?