In pain and confused

Me and my current boyfriend have known each other for over ten years, we’ve been childhood friends. We have been dating for about six months, I had emotional issues and he’s been helping me through it and he’s been helping me a lot. He was very sweet and caring, but as time is going on he seems more distant and less caring as he used to be and he told me that he has “something to tell me” and it would affect us based on how I’ll “take it” but he won’t tell me. Honestly I really like him and I’m scared he’ll leave me and the thought brings me to tears. I don’t want what we have to just be left in ruins. Does anyone have any advice on what I can do to save this? I don’t want to go back to how I used to be.