Im struggling to cope with my boyfriends mental illness?

About a month ago my boyfriend was diagnosed with psychosis and im finding it very difficult to cope with the ups and downs of his condition, he was a very fun loving bubbly guy and now he's withdrawn, snappy, and very irritable, like last night I came home and he had came in from work and tided our whole flat after doing a 12 hour shift, he didn't even look at me and then told he he was going away to get juice, he disappeared for over half an hour (the supermarket is literally 50 yards away from our house) and came back in and said he neaded to clear his head.....its silly little things like this that are really getting me down, im not a very confident person so I find it very difficult to talk to him about anything and I feel bad because when i do i get very upset and end up crying and not being able to tell him how i feel, I am sooo worried about him but I feel like Im making him worse by getting upset and i just want to help him. He visits a community mental health nurse one a week and he used to smoke cannibis but since he was diagnosed he stopped. I dont know what to do and feel like im watching the man i love fall to pieces, i keep saying im fine to all my friends and family but i feel exhausted and feel like i cant talk to him incase i upset him and i cant talk to my friends and family incase i upset them. someone please help me