Yellowy snot like discharge?

HHE • Married to the love of my life 💕

My husband and I had sex without a condom yesterday morning and today when I went to the bathroom I wiped and there was what looked like yellowish snot on my paper. It was thick and I could stretch it between my fingers like thick, milky snot. I'm three days out from my period, took a 5 day prior pregnancy test that came back negative and we're both faithful so no STIs.

Any idea what it could be? I've never had this come out before. Could it be leftover semen?