What makes a guy open up and share their innermost feelings?

My boyfriend is really starting to open up to me and express his feelings to me. He called me up at 2am and aplogized to me and told me he's sorry he hasnt been a very compionate person in our relationship he has been going thru a lot with his daughter and his daughters moms drama and he told me he knows that I truely love him because Im still here for him and I had never thought he was less of a person because of his woes. He told me he had a daughter since the first time we met. He has a daughter from a past relationship and has never told his previous girlfriends he has a daughter and he told me he has been hiding his feelings but he told me he has a stronger bond for me and a deeper love for me now, he even told me that he cries to hisself about me and says he is sorry. I told him I understand and Im glad he expressed this. What makes a man feel like this?