Don't finish and ejaculate.
You're repetitively training .. habitualizing .. patterning .. yourself (and some really complex psychological and dopaminergic-synthesizing mechanisms, ventral tegmental area, etc, which I think you know this stuff) to expect and do exactly that ... to 'go about ten minutes ..or so.. and then finish and ejaculate'.
Change the tune ...
Go half an hour and don't finish. Go for five minutes and then just suddenly stop and go make a sandwich. Go for an hour and don't finish. Etc. Change it up.
Going to eat a sandwich, or chocolate .. to be more direct, can be an important re-patterning exercise since your body is expecting some manner of dopamine reward from the sexual activity, and dopamine's a -powerful- neurologic driver. You probably have the willpower to go off it 'cold-turkey', but if you need help ... food also causes it but isn't tied into the same behavioral rut.
(You might even be able to manually 'anchor' the neurology of not-finishing by simultaneously rubbing your nose, or pulling your ear, whatever, .. don't want to get into all of that right now, you can find info on it under stuff like NLP and (because your type of patterning here is also including functionally negative judgments about your ability and/or your body) maybe look up The Inner Game of Tennis -here- or -here-.
And .. work-in not only some 'rest-sets' .. where you can relax and de-escalate for a few moments (in actual sex this could be stopping to kiss something, or to switch positions) but also work-in some 'pacing' .. where the escalation never goes too far in the first place, and some 'reverse-kegels' too.
edit - added this [ ♫
Relax, Don't Do It, When You Want To Sock it To It... ♫ ]
Long ago, some chick told me after sex "wow, you're totally not just in it for yourself" .. cos I was into rocking their world and didn't care if I came or not ..
Later on I discovered that -saying- this ahead of time was like a magic wand for completely eradicating what people later named 'LMR' (last minute resistance,
link from web) and will get you in-like-Flynn on a first date. Don't abuse that.
But you have to kindof mean it .. and be able to back it up. Patterning to always go ten minutes and pop your cork isn't going to back it up, -- patterning to go for as long as you want and not care whether or not you pop your cork is how to back it up.
Physiologically you only need to clear your pipes two or three times a week anyway, ... more than that begins increasingly to tax the endocrinology and nutritive upregulation of the HPTA through excessive 'prolactin rebound' and
pretty much this from the web (save me some typing. That's a huge page, I'm only linking its first paragraph)
and eventually even this(!)