I can imagine it’s very difficult to feel this mistrust with your boyfriend, particularly after you’ve felt so close.
To try to police his every action will be draining. Once you do not trust the person you love, it starts consuming your time and energy. Every moment invested in checking up on them ends up increasing your sense of insecurity. It may be more productive for you to keep talking to him directly about what you need — and to keep asking him what he needs. You are a young couple and learning how to discuss ways to help, rather than hurt each other, is an important skill to develop.
True intimacy involves couples being able to be mutually vulnerable. I encourage you to find ways to work with your boyfriend, not run yourself ragged checking up on him.