40 minutes of sex is actually quite a bit. I believe the average for guys was something like five minutes during sex. So your guy is by no means abnormal.
Most girls take longer than their guys though, so there are a few extra things you can do to prolong sex.
1. Thick condoms: Thicker condoms dull sensations and make many men last a bit longer.
2. Warming lubricant/condoms: A lot of guys also claim to have dulled sensation when using a warming lubricant or when using a warming condom.
3. Lots of sex: Once a guy has an orgasm, he usually can't have another one very soon after. So you can have sex, give him oral sex, give him manual sex, or tell him to masturbate. Then you can try having sex an hour or two later. That's enough to make most guys last a bit longer. It sounds like you've tried this, and it hasn't worked for you yet. If your guy is young, that's probably the reason. Younger guys can usually have orgasms closer together than older guys. So this technique might work better in a few years!
4. c**k rings: Despite the vulgar name, c**k rings are great for many couples because they help guys keep erections for longer periods of time. They're also pretty inexpensive.
