It sounds like you need to set some expectations and boundaries on communication together. Let him know you’ll honor his need to time away as long as he lets you know that he’s going away for a few days. Because you worry that something has happened to him. Marriage is all about give and take. If he’s struggling with PTSD, this time away is likely necessary for self-preservation.
It does sound like ADHD could be at play. Although, the effects of PTSD on daily functioning could look like ADHD. Anxiety can also look like ADHD. The bottom line is that he needs a professional evaluation to determine exactly what is going on and to get treatment. And, if he’s not ready and willing to explore that, there’s little you can do to change it at the moment. You can absolutely set boundaries and expectations for your relationship though — just be sure it’s a 2-way conversation with both of you compromising to meet in the middle.
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism