Good grief, when you said he had a dodgy past I was expecting stories of a criminal nature. So he's got up to some stuff, there's plenty of skeletons in my cupboard, difference is I dont feel the need to share that info with new boyfriend, if they ask, I'm honest but they dont need it in their face. I think he's been showing off to you, sounds pretty immature to me. As the others have said, have a chat to him, let him know that you dont want to hear anout what he got up to with other girls. It's not very nice for him to have all these texts on his phone, but I wouldnt suggest he deletes them-that might set him off, I know I woudnt like it if asked. Crete asks a good Q-how long have you been with him? If its a long term thing I would think he should be deleting them without you having to ask. But this is just my opinion-it's not necessarily right!
Dont think about the past, what's done is done, concentrate on you too. Dont be a prude about the porn, join in, but if you dont feel comfortable with that, just accept that he is a man and therefore will watch porn. Its the law. I would suggest if his pprn viewing is interfering so much that you're not getting enough actual sex then it is a problem and he should take a look at himself. Good luck