How big is too big for a blood clot?

I've passed three and I'm also not even on my period. Just random blood clots and they seem pretty big, (obviously coming from my vagina.) I posted a picture earlier and people said it looked like a miscarriage but I don't think I was ever pregnant. It's just strange that I'm not on my period and not having other bleeding (besides a tiny bit of brown discharge) but I'm getting these random clotty things/globs.