Because you bled, doesn't mean you are pregnant.
It could have been rough sex and just irritated your cervix..
If you are pregnant, as for knowing by whom, it is impossible to tell... Having sex with more than one partner during a two week span could result in either being the father...
Do you know for sure if you are pregnant? I would say if you are it's more than likely the first guys because if you just slept with the other guy this week it wouldn't be long enough for you to even know your pregnant yet.
You wouldnt kno till a dna test are you for sure preg?