Over the counter your choices are usually pretty limited - Viagra (and pills like this) can help, you may still finish quickly on your first round but your rebound will be a lot quicker . Other than that you would need to speak with your doctor.
There are a few things you can do naturally that may help - what about getting off before your gf arrives, this may make your first round last a lot longer? Then there is the start stop technique that you can practice - pretty much self explanatory, when you feel your about to cum stop, let the sensation leave and start again. Some people use the squeeze method - Most commonly, the "squeeze technique" is used. If a man senses that he is about to experience premature orgasm, he interrupts sexual relations. Then the man or his partner squeezes the shaft of his penis between a thumb and two fingers. The man or his partner applies light pressure just below the head of the penis for about 20 seconds, lets go, and then sexual relations can be resumed. The technique can be repeated as often as necessary. When this technique is successful, it enables the man to learn to delay ejaculation with the squeeze, and eventually, to gain control over ejaculation without the squeeze.
The biggest thing on this is to relax and not over think it - the more you worry the more your going to be super focused on cumming and will make matters worse. Have you tried to change positions?
