I think that this is too late for implantaion bleeding, if u were going to have implantation bleeding (not everyone does) you would have it 6-12 days after unprotected sex. But im pregnant 9wks 4days and i didnt know for a long time i was as i have been bleeding on and off since about a week after i conceived. Even had a light bleeding round about my period was due which i thought was my period. But saying that, although the 2nd was ur fertile day, it IS still possible u cud have fallen pregnant on the tenth, meaning it could be implantation bleeding especially since u have missd ur period. Take a test. Gd luck, Let me know how it goes. xxx