Longer sex

Yes, there are a lot of them, but they all come down to the same thing - basically knowing to block your orgasms.

While masturbating, bring yourself close as you can to an orgasm as you can without ejaculating then stop for a minute and start over. After you get enough practice in being able to block your orgasms 5-6 times in a row, try doing the same while your girlfriend's  giving you a hand \ blow job. The while having sex.

Also, a nice thing would be to just very your sex life a little bit, have sex in penetration, stop and make out, or go down on her while you take a break and then go back into penetration. You'll both have more fun.  

if you suck at sex, then that sucks.  Maybe you should try some lovrub .  My girl loved it.  It gave her so much pleasure, she was orgasming quicker then me.  She had two before i had one. 

There are a few ways to last longer in bed for men, but I recommend doing kegels (for him). They're very easy and really help with strengthening orgasms and staying power.

Another good strategy for lasting longer in bed is to maybe consider having him take a male enhancement pill. This is basically an herbal supplement. There are many herbs which can help a man's sexual stamina. Men around the world have used natural herbs for centuries to improve their sexual performance.