what’s the big issue about sexting?

The only thing matters on this is that how old those messages were. And if you did it after getting in relationship with the guy then its wrong as hell. And if it was really a long time ago then I wonder how the hell did your boyfriend even get to know about those messages.

He could be seeing this as an emotional affair. Just because you and another person are not physically having sex he many see it as an intimate sexual/emotional relationship of another kind with someone else. This is something you're really going to have to talk to him a little longer about and see what his true feelings are. You may have crossed a line that he's not comfortable crossing and you may have cheated in his eyes.

I don't feel that this is similar to porn as there were two people actively communicating where porn is a one way communication. He might be more open to sexting if you're sexting with him and it could spice things up in your own bedroom.

I see your point, to be honest I don't really see an issue with that either. Just be careful to make sure that you trust the person you're talking with.

It is not a huge deal, depending on the situation. Sexting, like all other conversations, should be done carefully. Only talk to people you know, try making sure there is no minor to adult relationship, and make all of your intentions clear, (more so how you feel about the other person.) As long as you feel safe and comfortable, and the person you are sexting feels this way as well, there should be no problem.

I think the issue is that even though it is only words it makes them feel as if there is something lacking in the relationship or you would be having that dialogue with your partner. He may also think that if you are willing to get into sexual details over text that you may also be willing to eventually begin doing it with someone else.

Screenshots. =_=