What should I do as an 18-year-old female? Is it a good idea to look at my boyfriend's phone, who is 19?

Hey everyone, my boyfriend (19M) and I have been together for three years, but he cheated on me (18F) in the past. We broke up, and after some time apart, we saw enough progress to give our relationship another chance. Since then, we've been happily dating for over a year without any repeat incidents. However, I've recently been feeling a strong urge to check his messages, something I've never done before. Should I go ahead and do it?