https://www.mangago.zone/read-manga/lucky_paradise/
i thought this was a cute story at first but its so angsty and exactly what u wanted. lmk what u think
https://www.mangago.zone/read-manga/hina_wa_mitsuiro_no_koi_ni_torawareru/
I really love this manga, i don't know if you already read it or not
https://www.mangago.zone/read-manga/bj_alex/ (webtoon, literally what you described)
https://www.mangago.zone/read-manga/itonaga_kun_no_koi_no_ito/ (manga)
https://www.mangago.zone/read-manga/ways_of_parting/ (webtoon, mostly similar to what you described, but not perfectly and super angsty. I won't spoil!)
https://www.mangago.zone/read-manga/love_me_doctor/ (webtoon, literally what you described)
https://www.mangago.zone/read-manga/love_works_in_mysterious_ways/ (not a long seperation, but lots of regret!)
I want to read a manga that has a seme regretting his actions for what he did to uke. Any Recs will be appreciated and also maybe mangas that has like unrequited love and the reunites later on and loves the uke/seme or something like that