The behaviors you are describing are indicative of your partner being controlling and fringing on abuse. I get that he has romantic notions about being the only person who cums or has cum in you, but he is NOT acting in your best interest.
The most important reason for a person to be on PrEP is being a negative partner in a serodiscordant relationship. I know he is undetectable, and I know U=U. But to have his meds be the ONLY barrier between you and contracting HIV is simply negligent in a world where PrEP exists. Accidents can happen (eg he forgets to take meds or bring them on a trip). Also, people can become resistant to meds over time. Normally, this isn't a big issue; his doctor would just adjust meds at his next checkup. But it would be a huge issue, if he infected you while his meds were not working.
The second most important reason to be on PrEP is having sex with multiple partners. The CDC and WHO both recommend ALL men-who-have-sex-with-men who have multiple partners to take PrEP. "You don't take loads from anyone else" is not a justification. There are enough stories about broken condoms and stealthing on here to make that point. The majority of people I personally know who are poz became poz when I condom broke usually with a partner who thought they were negative at the time.