Didn't have a period for 2 1/2 months and now I'm bleeding bad whats going on?

I was bleeding really lightly for the first day and half now I'm bleeding these huge clots. I'm not sure whats going on. And I didn't think I was pregnant. Because my periods have been different since I had my baby 9 months ago. But I never missed a period before I was just having them twice a month. Please help I don't know whats wrong.