I'm sorry for this question, I know it is rather explicit but I don't know where to turn.
Anal sex is enjoyable for me as long as somebody has a moderately short penis. If i try to take something longer I get an extreme stabbing pain deep inside my guts that is radiating into my lower back. It gets worse with more pressure. I thought this was normal for a long time. I believed that I am just "untrained" or "don't relax" because I do not bottom very often. I'm starting to realize now, that relaxation or a lack of training or lubricant is most likely not the problem here. The pain when that is the problem is quite different. The web is full of superficial advice that always blames a preparation or relaxation. What else could be the reason for this pain? I really wish I could enjoy anal sex.