Hey Stipe, here are some ideas:

Have sex more often!! You should find the control of enjoyment comes naturally

Relax about it - the second you worry about coming too soon, it's gonna happen - life's like that! Explain to your partner that you want to have sex for longer, and perhaps as a means to doing that try "repeated" sex, whereby you have penetrative sex with no pressure on time taken - perhaps perform cunniligus on her for a while when recovering, then go again, again with no pressure, not caring if it only lasts 30 seconds. You should find that this helps you.

You could also try altering rhythmn. When you can relax a little, you should find that you changing it will alter your sensitivity. Banging straight in there of the bat will ensure a quick discharge, start slow, gradually increase, return to slow, perhaps withdraw altogether for a while and use your mouth (& not just on her pussy).

The classic is to come once before you have penetrative sex, on your own or with her help, but I would recommend doing the above instead, as you will get better control over your sensitivity.

Also, don't be afraid to ask about her levels of sensitivity, and what suits her best.

All of these should help a little, above all, just remember to enjoy it, it's not a competition and there are no prizes!