when u last only 3 mins and 59 seconds at sex. and you gf is mad at you...how u feel????

That's because you are rushing it and you are not doing a position which can satisfy the two of you. Get her to be on top instead of you in control, so that she is satisfying herself. Then afterwards, you can get yourself satisfied. I don't blame your girlfriend, you should be giving her a chance to be satisfied too. Not just getting yourself climaxed and then thinking "that's it".

"Control! Control you must!" (Master Yoda).

1) Whenever you masturbates, try to "quantize" your sexual heights.

for example:

Level 1 -- You just have a "tingling" feeling.

Level 2 -- You are high, but can still go on for at least a minute or two.

Level 3 -- Approaching 4, but if you stop now, can go back to 2 or 1.

Level 4 -- the "Point of no Return".

Level 5 -- You orgasm.

When you know yourself better, learn to stop and take breaks. If needs be, even get off the bed and make yourself a cuppa. (When you return, you're ready to go again.)

2) Learn to use your finger and mouth. Yes, Fingering may give her a g-spot orgasm (she assumes doggy style), while oral on her Clitoris and vagina (Missionary) may give her a Clit-O.

3) Don't penetrate her until she asks you to. She could be moist, even wet. But some woman simply takes a long time. So use your mouth and finger until she asks you to PIV.

To conclude: Give her an orgasm BEFORE you penetrate her. This ensures her smiling and happy with you, especially if you could give her multiple.