Yes yes...my boyfriend has the same problem, well not quite, but similar. He only lasts about 2 minutes, but can get it back up for a second time and then he can usually last longer. Here's an idea:
Read about tantric sex! This has helped my bf a lot! He has learned how to orgasm without ejaculating and can therefore sustain the erection (while it continues to be pleasurable for him!) This is only through masturbation, but he is trying to make his way up to sex eventually. It's taken him about 1 month to get to this point, and the book that it takes about 6 months to master for sex.
Anyway, since I can't tell you about how to learn tantra, I suggest looking it up or buying a book about it. Good luck.
P.S. Maybe even masturbating could help you last longer, or have your wife give you oral or a hand job first.