Wonderful boyfriend with ADHD who keeps disappearing! Please help me understand this behavior.

Hi all. This is my first post, although I've been reading through a lot on this website for the last month. I have been dating a truly wonderful guy for the last 4 months. He told me right away that he has ADD and is working with a behavioral therapist. He seems very sincere about the therapeutic work he's doing. He's 51 and I'm 50. We're both divorced with kids the same age (who adore each other), and we're both busy professionals fairly wrapped up in our careers. I never experienced the hyper-focus dating period as others on here have described - I think we're both too busy for that, and maybe also just cautious due to our divorce experiences. For the first few months we saw each other pretty regularly once a week, and we talked every day, often multiple contacts a day through texting and email... we grew close and comfortable with each other, and I think really very happy. But about a month ago two important projects of his at work began to place more demands on him, and he began to feel tremendous pressure as a result. He became afraid and nervous that he wouldn't be able to succeed in these projects. He feared for his future. I have been working very hard to put my needs on the back burner during this period, and to be supportive. A month is truly nothing in the larger scheme of things. But for the past few weeks he has almost entirely shut me out. We saw a movie together two weeks ago and spent an hour talking and at the end of that I felt sure of his feelings for me, and understood that he was truly needing space to do his work. But he hasn't replied to a single phone call, email, or text since then, even when my car broke down, even when I wrote that I understood how busy he was and how much I wished to support him - but that I needed him to simply reply with a quick xo, even when I just asked him how he was doing and was he ok? When I saw him two weeks ago it was after a week of silence like this, and I told him that I thought his silence meant he didn't like me anymore. He was VERY surprised that I thought that and told me he thinks about me all the time.

What does this behavior mean and how do you suggest I deal with it? I want to support his work but our relationship is so new I fear he is gone when he's so silent. I'm just not sure if I should keep my distance like I've been doing, or if I should get more vocal or if I should just accept this as lack of continued interest and let him go. It seems to me that in his life the squeaky wheel gets the grease. I am just not the squeaky wheel type and I really very much want for him to feel acceptance and support from me while also honoring myself. I want to give him space to do his work, but I also want him to communicate with me to some degree!

Please help! thank you so much!