Yes, you can give him herpes through oral sex. Even when there are no sores present, you are still carrying the virus and can pass it on. However, the virus is most contagious when there are sores present, so you should never have oral sex at these times. At other times, use a condom during fellatio and a dental dam during cunnilingus to decrease the chances of transmitting the virus.

You may have given him the virus already. You and he can get blood tests for HSV-1 (the virus that typically causes oral herpes) and HSV-2 (the virus that typically causes genital herpes). However, these may not tell you what you want to know. If he tests negative for both viruses, great; you didn't give it to him. On the other hand, there is a very good chance that he will test postive for HSV-1, since the majority of people are carrying this virus. If he tests positive for HSV-1 (or HSV-2, for that matter), the blood test alone will not tell you if he has the virus in his genital region or if he merely has it in his mouth, as most people do. The only way you will know for sure is if he developes sores in his genital region and gets them tested by a doctor. If he does not get any sores, this is not a sure sign that he is clean, since many people with herpes never show symptoms.

Also, if the two of you are worried about your parents finding out you had oral sex, you don't have to tell them why you want to get tested. Just tell them you got a sore in your mouth and want to find out what it is. It's the truth, if not the whole truth.

If he is not showing any symptoms then probably he is ok and you don't need any tests, but like girlygirl said, some people never show symptoms.
Just be more carefull next time.