i hate playing unknowns

[billyjex]

here's a standard line for me but it just feels so wrong to call down from the turn. his raise screams I'm beat and I have no redraws.

I am MP w/ KK. I raise. Villian in CO is completely unknown. He calls. Both blinds call (they're unimportant) and we see a flop of:

10 9 7. no flush draw. Checked to me, I bet, all call.

6bb to the turn. It's an A completing the rainbow. Checked to me, I bet, CO raises.

Folded back to me. I just feel there's no chance I'm winning.. obviously I'm bitching because I lost, but is this call down standard?