He has a hard time opening up.

How do I encourage my SO to open up to me. He cries in front of me a lot but won’t tell me what’s wrong.... I just don’t know how to help him open up and know I’m here for him 100 %. Sometimes when he doesn’t open up to me I feel like I’m the problem and I just rewind my whole day and all of our conversation to figure out what I did so I can make him happy again. It’s terrifying not knowing if your the problem or if someone else is the problem or what is wrong.