Should I give him his space?

My boyfriend and I are really close. We tell eachother everything. But this time, he’s going through a tough time and he’s completely shutting me out. He won’t call and he won’t come see me. He doesn’t answer my texts. I call and he only talks to me for a minute. I really want to help him but how can I if he won’t let me? Why is he shutting me out this time? Should I just leave him alone until he comes around or should I keep trying to get through him.