Boyfriend being off with me?

We've been together 8 months now. Started off great. Recently been spending more time together as we were off work the same time. We went to a new restaurant and he said his head felt weird in the morning and he didn't know why. Then said he's been feeling off and anxious the past 3 days still not knowing why. We get to the restaurant and tried to order through the app but we couldn't get it to work. He got frustrated with it so I said it was fine we could order at the bar. He was quiet and really off. I tried asking him if it's me. He says it's isn't but gets angry everytime then says I need to stop asking him questions. I got myself upset thinking what changed. A year ago he was a different person. He met a woman on tinder and fell in love in a week. Why is he suddenly so anxious going to a new restaurant and so off with me. I can't ask anything or even know what to say anymore. They are just weird moments he has and then he switches out of it but then he goes cold again. Tonight I called him like I always do and he said he didn't think I wanted to talk to him. I said I told him I would. I tried making conversation but we sat in silence on the phone mostly until he asked what the matter was. I knew how he would react if I said what I wanted to so I said I was fine. He asked again and I said I don't know if I've done something or if he was just tired. He straight away started getting defensive saying no stop not having this conversation. I said fine conversation over. He said he didn't want an argument I said we arn't and then he said goodnight. I don't know how this relationship is going to last if he keeps being so off with me and can't communicate.