Help!!! Thread like red ?!

So I’ve been taking metformin for about 3 months now I had a period a month and half in of taking it now waiting for my second period . For a couple days now when I wipe I keep getting this ruby red stuff that almost looks like thread or string , it’s so weird and it looks super thin to be a clot , anybody know what it could be ( no it is not actually thread or string lol)???