I’ve got quite the dilemma and it would be great if I could get some help.
Heres a little back ground info.
I’ve been going out with my girl friend for a few months. We have just recently started "having" sex, and things have been going rough. The first time we had sex, things went good, with a little bit of awkwardness at the start. But overall it went well.
Our next time doesn't go as smooth. We have a long session of foreplay, and when we are both in the mood, I go for the condom, but as soon as I put it on, I begin to go soft .. 
And I am unable to get it into her. After trying twice, and not succeeding, we gave up for the day. This has happened 3 times now, and I am starting to get really worried, plus my self confidence has gone down the drain.
Basically I can stay hard, right until I put the condom on, then I start to go soft. Is there anything I can do? I'm desperate for help.
definatly have her put it on or get a pre lubricated condom..those are excellent and keep you hard.
BRANDYE IS 100% CORRECT!
Let her put it on you...it will become part of the foreplay, and she also gets to decide WHEN she wants intercourse!
Oberon's tip is correct too.....get theright size condom and put a bit of lube on yoru cock before u put on the rubber!
Putting it on with your mouth is fun...
Just be careful and don't bite the condom...lol. (advice for her, in your case...lol)
Try a different condom. I have a problem with getting regular condoms on and that usually means I lose some stiffness. I have tried the Trojan magnum size and they go on much easier. You might also try a little lube on you and inside the condom- ky jelly or astroglide should be available to you- as this sometimes helps the condom go on easier. Just make sure whatever you use is water-based.
I hope this helps. Good Luck.
In my condom days, I usually put it on him. Make it part of the play and there are lots of little ideas that can make things more interesting.