I posted this yesterday so I am copying and pasting :
How old are you ? Have you tried playing with your fingers or dildos ? If so , do you get a boner while fingering / self-boning your butthole ?
Every guy is different , some bottoms get erections while being penetrated , whilst others don't . In my personal experience the bottoming experience is more thrilling and pleasurable when you get a boner and start pre-cumming while being boned ( but that's my case )
I guess from what you've posted you may not have tried a
dildo
It hurts the first times , specially if the top is hung
First of all , you must make sure you're clean inside , wash your hole to avoid unpleasant surprises . I think it is very important to be physically attracted to the top to stand the initial pain , if he is a passionate top , in my view , he should first rim you and get you very aroused , then you would need to have plenty of lube to initiate the penetration , if you feel the beginning of the penetration is too painful you could make him lay down and you could slowly and progressively sit on top of him until getting used to his dick , then you could switch positions and he could switch to a faster pace of thrusting .
Is he an experienced top ? if he is an experienced top who knows how to please another guy without causing him pain , he should know what to do
Even when one has bottoming experience and you get involved with a tough careless guy , he can make the experience painful if he is tactless , rough and selfish only focusing on his own pleasure while inflicting pain on the bottom ( if he is that kind of top , it's better to cancel the mission )
Get to know him well , so you have a pleasurable and memorable experience