What is this? Passed during period

I am on the patch birth control but didn’t put it on consistently like I was supposed to. So a part of me is worried it could be miscarriage but I don’t want to assume. I had a period September 11 and another two weeks later at September 25. I just realized I hadn’t gotten my period for a while. This has happened before, I have passed something very similar once before. I assumed it was a miscarriage. I didn’t realize I was pregnant then. Anyways, I guess this is just as clarification. If anyone else has experienced this. It was not breakable.. solid and whole and white stuff in the toilet I am unsure about also. I thought this was my period.