first time in a serious relationship?

I've talked and went on dates with many guys but never looked to be in a relationship until I met my now bf of two years. I sometimes get offended by some of the comments he make. He says in all his other relationships his exes never cared about him texting females all the time or what he was up to. He said it's my lack of experience to why I act that way ? 
I caught him texting sex things once to his friend and it took me like min to move on from it and he said If I had any bad relationships I would realize that sexting wasn't as bad... Which I know compared to most but damn my feelings are still to be validated .