Assuming give head, blowjob, bj, fellatio, oral sex...

It is sex. Notice the word "sex" in "oral sex", ok? It is there for a reason.

You will not gain anything by doing it and might suffer various losses, be it via exposure to disease or feeling crappy afterwards. So, no point. Hopefully he will like you. That he talks to many other girls in no way shows that he does not like you. Time will reveal whether he does, indeed. Just be patient, do not drink too much and always eat eat eat while drinking alcohol.