Possible to get pregnant in this position?

Nope, any position will do the job. They do say to be in the missionary position but seriously it could happen in all positions. Just try to make sure you keep "the stuff" in you for a while afterwards. You don't want to be on top and then run a 1/2 marathon. You'll want to lay down for a bit to make sure all the sperm don't fall out and have the chance for them to swim up. Good Luck and I'm sure you're chances are great!