I had the same thing happen to me at 32 weeks I don't think its your mucas plug, my doctor didn't seem concerned when I asked him about it.
It sounds like Discharge. Mucus plug is elastic and clear and progress to slimie, clear, tinged with blood.
It's probably pieces of your plug. I have the same thing and I'm not having sex Even then then I didn't have sex, the stuff your describing is what generally leaks out for me to the point I need a pad to get through the day. It's completely normal ask your doc the next time you go in to be checked if your plug is there expecially if you keep leaking the yellowish mucus. I didn't have a bloody show or giant plug come out mine was in pieces. So I never knew till I asked if it was still there
It sounds like discharge to me. Totally normal.
It is sperm. It comes out of me the same way. Like snot. I am 4 days away from giving birth
And it didn't have blood mixed in