Well I'm sure that you know, it only takes one sperm in order to hook up with your egg. Men have pre ejacualation.. so the chances are very, very high.
I Know there is this pregnancy test called First Repsponse. It states it can detect pregancy at least up to 3-5 days prior to a first missed period. How true that is, I don't know. But they are a big name. So maybe they have a good product. But we play a part in that too if our HCG level is hight. I saw it at Walmart you may want to read the package and check that out..
Awesome no medications on the test.. I think you should be just fine as far as that is concerned.
I know the worst of any pregancy is the waiting period. But if it were meant to be.. there is no changing that course of being or not being pregnant.
Good luck.... let me know thru PM what you do find out..
If you have any other questions, please feel free to ask.