Hi Lia - the answer is actually in the footnote to your OP question. The most likely answer is because he has a small penis. And if I was to guess his size issue is to do with Girth. My question back to you is when he enters you, can you feel much after 2-3 minutes? If not then nor can he. And without having friction against each other its very hard to orgasm.
I learned this with my recent wife. After quite a few partners over the years where I could really not feel much at all and thought we were just not a good fit for each other, she was brave enough to bring up a question about my thickness (as she called it) and if there was a way I could do anything to increase my girth because she could not feel much at all (she had just recovered brilliantly from breast augmentation which was amazing for us both., She wanted this after giving birth but also identified that prior she could feel about 3/10 for what she wanted, but after her recovery from bearing a child she couldnt feel me at all. And it was the same for me.
We were open with each other and she suggested measuring me against what is publicy out there on medical studies and forums. Cutting to the chase we both found out that I was very very thin (low 7th percentile) and then reading on from that it all came out between us. I had to deal with my past and she had to deal with a hubby who has what they term in a lot of forums a pencil d**k. Its common for both partners to not really gain much satisfaction if the male has a very thin penis. There is a lot out there on it if you want to read further.
For me it was actually really helpful and not humiliating. We use sleeves which was fantastic for us both and we can enjoy it much more. We also both laugh now once the sleeve comes off and talk naughty about stuff that borders on teasing which I really enjoy. Most of all I really enjoy seeing my beautiful wife enjoying sex and im now able to orgasm too as I can feel her with the sleeve on.
Its been an interesting journey. I always wondered why it was easy to climax on my own (no I never had a death grip) and almost impossible with a partner. I think its likely, now I look back, that quite a few relationships failed because of the sexual part of those relationships life.
If you mentioned in your post he has a small penis then you probably already suspected. Well you were right. Now you just need to be delicate at the start of the conversation and then have fun with it. My wife and I have moved on to even more exciting things - but that just depends on who you both are and your relationship.
Its an interesting topic and journey. I dont agree with one poster who said that if he is a nice guy thats all that matters. Thats old school thinking. Sex is a major part of a relationship. If your guy has a small penis and cannot climax insode you then there are loads of things you can do to change it up and make it so much better. PM me if you want advice. Happy to help if I can. Wish you both all the best.
Cheers
MattyHubby