Stomach pains usually last about 24 hours and go away, they're terrible but there isn't usually much you can do about them but let nature run it's course. Doctors don't really prescribe anything unless it's been going for a while because of the short time and the non-lethality. However, that being said there is an over-the-counter medication that can help quite a bit called Buscopan (Butylscopolamine (use this if your chemist doesn't know what Buscopan is)). It works by relaxing your stomach muscles which stop cramps and spasms that cause the severe pain, unlike most medication Buscopan doesn't simply mask pain but it actually stops the initial cause of the pain. It can be very helpful when you're ill and I strongly suggest you buy some to keep in case you feel ill again.