[lakers fan]

hi, my girlfriend and i have been together for a good while now, and we have stopped using condoms. The sex has been great, but there is a problem, i now cum was too fast when having sex. i feel real bad because i am not always able to get her off because i have cum so quickly, and i spoil the mood and she gets quite mad with me. So i guess im asking, is there any tips on how to last longer, without cumming too fast? any particular lubes or anything? any advice would be helpful thanks.