Two things:
1 If you wear a condom, the sensitivity is reduced (some have this as a special feature) so ejaculation may be delayed. Not to mention the pregnancy/STD issues!
2 Look up the "PC" (pubococcygeus) muscle on the internet, here's an example:
PC Muscle - AskMen.com
You can work on control using this - practice while you're not actually having penetrative sex and see if you can keep yourself from coming - it works!
I was actually having a very interesting conversation the other day with a female friend who told me that her experience is that men take longer to come as they get older - which can be annoying in the other direction sometimes!
Best of luck.
KP