Why do I feel like this? (Long post)

I was absolutely in love with my boyfriend. Lately though he has been getting on my nerves. He doesn't understand my feelings for anything. He says I get mad at every little thing & doesn't get why I don't like the choices he makes. An example of this is he works 3 pm - 9 pm one day. Stays up till 1 am, then sleeps the entire day till 1 pm when he has to get ready for work. He doesn't talk to me or spend any time with me & wonders why I get upset. If I try to talk about it to him he says I am getting mad over nothing. I love him but lately the words "I love you" are starting to feel like empty words. I went from having a dream of marrying him to not being sure about anything. Why do I feel like this?