Young males, in particular, are apt to premature ejaculation. I believe I have admitted that on my first time I began ejaculating on my second stroke - what a bummer! Fortunatly, I got better over time, so give him a chance. Attempting to hold back an orgasm is not easy, but it is easy for women to complain and ridicule these men. But, at times, NOT reaching an orgams is at least as difficult for men as it for some woman to actually be able to reach orgams.
He will most likely improve with experience. What he needs to do, though, is to concentrate on you and make sure you are being pleasured. This can be via manual or oral activities, done before he beging intercourse.
To help him last longer, some options are for him to masturbate earlier in the day; use condoms; apply a delaying cream such as Mandelay, sold over the counter in pharmacies, including Walmart; or to use any of the other techniques frequently discussed here.
Help him out, encourage him and support him, and he will be fine.
Let me add that you see rather naive about sex - you don't even know if he has orgasmed for sure! Do some study on this and learn - make sure you always use condoms, and be aware how you can catch STDs.