You can not get pregnant if a guy eats you out.
Unless, perhaps, he ejaculated, took the semen into his mouth, and then spit it into your vagina like a trained seal.
Therefore, if you see a guy drinking his own semen and then spitting it out in a fountain across the room you should strongly consider whether or not you really want to have oral sex with him.
Of course, if you were practicing safe oral sex, this wouldn’t matter, since it would just hit the barrier, bounce, and he could swallow it himself. I don’t know that I’d want to have sex with anyone who practices being a sperm seal in his spare time, but your mileage may vary.
Explanation for why you can not get pregnant by being orally pleasured by a person of either gender:
People’s mouths do not contain sperm. Without sperm, there cannot be pregnancy.
In fact, there is no fluid that comes out of man that can get you pregnant except for his semen. There is no fluid that comes out of a woman that can get you pregnant at all.