A little advice, please

I’ve never posted on here before so I do feel a little awkward. I hope it makes sense.. it does involve my period, so a disclaimer that it is a little gross.

My period is typically regular, it has been for years. In July, I was 11 days late so I took a pregnancy test, which showed negative. I have one daughter already, and I didn’t recognize any symptoms like I had felt with her, so I didn’t question it. My period did come, but it was light and spotty and lasted only a few days.

I got my period again the following month (I think), once again very light and spotty to where I needed nothing more than panty liners. I normally have a heavy flow. Only lasted around 4 days.

Fast forward two weeks later. I woke up with blood on my pajama pants unexpectedly and going into the bathroom there was a clot in my underpants. It was formed, thick and I couldn’t really pull at it. I have very intense cramps and I’ve been passing similar blood clots the last two days. Having to go through pads with heaving bleeding and then clots. I’ve never had this before so it’s struck concern because I don’t know what to think of it.

Has anyone had anything similar before? I haven’t taken to the internet to try to diagnose what it could be, so any personal input would be appreciated.

*I have been sexually active, always with a form of contraception (condom). Only one pregnancy test was taken in July.