Sorry if TMI :)

I've been taking 1 gram SSKI for over a month now. About 2 weeks ago I had my period, and one day I got an awful period pain for a few minutes before it left. It felt like something was ripping out of my insides. Less than an hour later I felt something fall out. Turns out it was this dark red thing, like a big blood clot but very firm, almost hard. It was about 3 inches long and 1cm in girth and it split into 2 at one end. It was horrible, but I'm glad it's out!! Anyone have an idea of what it could have been?