What is this?

Is this left over semen? My boyfriend came in me last night. Or is discharge? There was quite a lot of it that you could see i was like "wet" from the outside of my pants. Im only 17 + 5 days so i want to make sure this isnt my mucus plug or my water breaking or something

and that i am not going to go into pre term labor. Sorry if this sounds silly, i just have anxiety.