Blood clot or fibroid?!

Is pretty descriptive but would be seriously helpful to get some insight.

I have had the implant put in about a month a go and have been spotting ever since. Recently my GP has given me the progesterone only pill to reduce the spotting but it’s become heavier.

But today, I had a tampon in today and when I took it out, there was a hard flesh coloured ball, a bit bigger than a size of a pea and it had a thick stringy bits hanging off pretty much the length of my tampon? It kind of looked like the shape of a sperm. I’m very confused, is it a blood clot or a fibroid?