trust issues

basically my boyfriend had done something in the past that has really affected my trust. every time i ask him if he’s doing something he’s not supposed to he always says he’s not but due to those past problems i don’t believe him. do you think it’s too much to ask him for his phone? to reassure myself that he isnt lying (or he is who knows). or should i just suck it up and try to push the thoughts out and believe he’s telling me the truth. send help AHH