Hi Doctor, My Name Is Tom, I'm 24 And Gay

hi doctor,
my name is Tom, i'm 24 and gay and had been experiencing anal sex for a several times, and everything was fine. but a while ago me and my partner have sex and after that i've been feeling so uncomfortable with my anus. the symptoms is i felt pain only in my sphincter an whenever i clench or tighten my anus it hurts, and also when i have to go number two. it bothers me because i'll always feel the urge to go to the bathroom more often then usual, and there's not much of feces that comes out even when i still feel the pressure inside my tummy. so what could i have? and what should i do? thank you