You're probably fine, spotting after sex is normal, but I would call your ob to be sure.
If you are worried call your dr that's what they are there for, but it can be normal to have some spotting as long as it's not a lot and it stops. If you don't call sooner bring it up at your next appointment just for ease of mind.
This could be a low lying Placenta. Being that it was bright red.
I'd say a little bit of spotting after sex isn't a huge concern but Idk about the slimy thing :/ that's scary! Are you crampy or anything? I'd call your ob just to be safe.. that's what they are there. Your scans 2weeks away and myself would worry if I didn't make the call.