Pregnant after having your period?

So I just finished my period, I had my terrible two first days and it just kinda abruptly slowed to nothing. Now I'm pretty sure with the amount of blood that came out of me it would be impossible for anything to survive but usually after my period, my hormone levels are back to normal. But I'm so tired and moody, which is how I am usually while I'm on my period. I'm probably just being paranoid but could it be possible?