I agree 100% with 40smama. It can mean so many different things, and most times it's just fine. But I really think any bleeding should be checked out sooner rather than later. Besides, it will help put your mind at ease. Otherwise you will probably sit and worry the whole 3 weeks, and thats no good for you or the the baby.
Good luck to you, I hope all works out!
I had pink spotting at 9 weeks but it was several hours after b/d. I think you should contact your dr & update him on what's going on. Three weeks is an awfully long time to wait to find out anything. If you're having sex, I would wait until you talk to your dr. I don't blame you for being nervous. After it happened to me, I was a horrible wreck! Good luck and keep us posted.