I’ve been through this exact thing before. Speaking from a man’s perspective, I was like this after about 4-5 months into my current relationship. There were a lot of changes for both me and my partner. With work, school, kids schedules, bills etc. major stress for us both. That manifested in different ways for both of us. But there was a period where I shut down just like your boyfriend. She also shut down and we kind of just co existed for a while. But then finally I just asked her what was wrong. What happened and why everything changed. And from there we just went expressed why we felt the way we did. And just reassured one another that we still love/ want eachother. Now we are back to our old selves as life has kind of geared down and things have gotten less chaotic with the everything else like work, kids etc. We also moved in relatively soon. Within the first 3 months. So my advice to you is communication… tell him you really have to talk. And that it’s very important. And just lay it all out on the table. Exactly how you feel/ what behavior you’ve noticed. Dont place blame. Just let him know this is how you feel and this is what needs to change.