Premature ejaculation

My girl friend wants to do sex with me,We are in a serious relationship and we will marry each other.But I have premature ejaculation.Though I don't know whether It will be a very much problem in future as I am feeling this problem since last 4 months only. Actually my girl friend needs about 40-45 minute foreplay,(kissing all over her body), then fingering(10 min), then sucking her vagina(10 min), but when I reach to suck her vagina I feel very much excited and rush to put a condom and then penitrate, but when I just touch my hard-penis to her vagina and give a stroke I ejaculate and I am still not able to loose her virginity . I am getting frustrated as I am not able to enter my penis into her vagina.This same incident has been happening since last 4 month.And each time when I put the condom I started to feel that I am just going to ejaculate and I can't break her hymen .Please help; I am ready to anything to get rid off this problem