HELP! It’s my boyfriend

So the first time we had sex everything was fine, he finished within 20 minutes which was fine. But the past 4-5 times he keeps finishing really quick, like less than 2 minutes. It makes him feel really disappointed and upset with himself even though I told him I completely understand and I’m not upset about it at all. I think he’s losing confidence, any tips on how to make him last longer? (Side note, he lost his virginity to me a few weeks ago so this is pretty new to him)