Definetely something that I have been dealing with most of my sexual life.
Early teen years masturbation was OK as I am able to have more control, start and stop, change the grip, etc
when I started having sex with guys that was for me a major concern and embarrassed me a lot, lot of social stigma around measuring the quality of you as a lover for the time that you last in penetration.
With my first long term boyfriend I use to cum quick in the first one, recover in less than 5 min and go for a longer second one and he was very similar on this so it was good.
after we broke up I was having lot of personal issues as with some hook ups (sex in a relationship is different as both know each other better and how to manage it). Sometimes I came just by the stimulation of putting on a condom. Other times just as soon as I penetrate the guy (I have been always more top than bottom).
during sometime (around 2 to 3 years) I used to wear my foreskin retracted, using a sillicobe ring to keep it back and my dick head desensitized a lot (in a good way), that make me gain lot of self trust and confidence and I used to last really good!
I was tired of the need of wearing a ring constantly (as my foreskin didnt stay back by itself) and also the ring get old so I stopped. Using a public bathroom or public shower was something that I always needed ro remember to remove the ring, putting it back, etc
My dick was back to previous sensitivity and then I started cumming in a short time again (not sure if this is real or just a psicological effect but it happened).
now I have a long term relationship and my boyfriends loves to make me cum fast as he considered it as a great reward of making me that horny in a short time that I cum this fast. It is not a problem as for him is hard to cum and usually he can only reach this point masturbating himself (obviously with my help and stimulation in other parts of his body) and also he doesnt have the need of cumming in every sexual intercourse.
For me it is a but frustrating cumming too fast and I have been working in doing kegels, that works to last a bit more but as soon as I relax I cum like a fountain (I need to keep the tension to not cum and I can only last doing it some minutes). Now I am 39 and my recover time between is longer, so I need more time than before, maybe something like 20 min to go for another round and obviously this makes the heat of the moment dissipate.
I have decided to go back to permanent foreskin retraction (for the pro-circ guys I have considered getting cut in the past, I really like a cut dick and honestly a high and tight cut looks amazing but at this moment is not my priority). So then I bought a set of sillicone rings (on ebay from South Korea, they look great and similar to the previous one that I used for years, this previous one was a japanese ring). I need to talk about this with my partner, he will be reluctant about it as he loves me to cum fast, but I will share with him (I already did it a couple of times) my thoughts about why cumming fast makes me feel frustrated.
so in my personal experience foreskin retraction on a permanent basis has played a great role, using a cock ring also works good for me, more if the cock ring has a separate ring for your balls so helps not letting them retract a lot and then that helps me in delaying the cumming. Kegels has also helped but I am not very good in keeping routines in my life but I will try to go for it again. If you like some anal play having a toy (or a dick!) in my ass while I am penetrating helps a lot in not focusing just in your dick and try to split your attention in other parts of your body.
as a last point is very helpful to see that I am not alone on this and very sad to see how society has make the best value in sex a guy that can last very long during penetration (instead of embracing the diversity that sex has)