I've Had Sex Twice, The First Time I Lasted About

I've had sex twice, the first time I lasted about 20 /30 seconds. I was gutted and depressed for ages afterwards. The next time I did it was less than 5 seconds, literally 2 and half thrusts. But when I masturbate I can last up to 5 minutes if I try, although I d say my average time is 1 to 2 minutes. I don't understand what I've done wrong. I don't masturbate to much, I think, twice a week Wednesday afternoon and Saturday morning, but that's only recent, when I was a teenager I kept it welĺ down ( 3 or 4 yes a year till a left coĺlege). I'm about 8 cms flacid and 13.5 erect