Do I still trust him?

I have been going out with my boyfriend for over 18 months now, he is my first proper boyfriend and I am in love for the first time. He came to visit me from a job up north the other day and was telling me about a message on his phone he almost sent me ranting about his housemates, but had decided not to send to me as it might make me sad. Whilst he was in the toilet I looked for it, but found a message he sent to his best friend at university instead, who is also my friend. It was a very crude message about a girl he is working with being “ a tease” and saying what he would do to her if she didn’t stop…you can guess it was along the sexual lines. I confronted him and he was on his knees begging me not to make him leave as I tried to throw him out. He told me his other housemate had said it, and he thought it was funny and sent it to his friend. I know this other housemate does like her, so it might be true, but I didn’t know what to think as it was highly immature and not at all funny. We have had problems in the past with cheating, mainly from my side which I am very regretful for now. I thought we were past it, and although he didn’t actually DO anything, it was his disrespect that upset me the most. Plus the fact that he doesn’t care what our relationship looks like. He actually went hysterical and lay on the floor and cried when I kept trying to make him leave and told me over and again he couldn’t be without me. I took him back for now, but it leaves a very bitter taste in my mouth. What should I do?!