Hi Erin,
It could indeed be anything. Last pregnancy I had a small amount of cramping and bleeding at around 5 weeks and nothing came of it. Healthy pregnancy.
Hang in there until tomorrow. There's nothing you can do either way except try your very hardest not to do too much physical stuff. (I know there's no point telling you to try not to stress.)
Sometimes even when not pregnant I bleed a little bit after DTD, so it could be that too. I think it could happen if your cervix gets 'bumped'.
Hopefully this reassures you a bit and I wish you all the very best for your scan tomorrow and for the rest of your pregnancy.