How do I tell my boyfriend I’m not happy anymore because I don’t get to see him anymore, and because he’s always on his guitar?

Talk to him when he is alone calmly about how you feel and express yourself. If he loves you he will understand and you will both work together to find a solution.

just express your feelings to him, just tell him how much you miss him, tell him how much you miss the time you both had together just tell him by seeing his eyes.Every one who loves their girl friend will eventually understand how much you miss them. Just be true and express your feelings. Also give him his time with guitar, he also has to spend some time with his hobby or passion whatever it is. Don't demand too much from him, he may start to feel the other way, that you are suppressing him and controlling him. just be you.

The best way to open up to your boyfriend is to schedule a good time to chat with him. Compare schedules and discover when would be the best time to reach him. Also, instead of telling you can also show your boyfriend how you feel. For example, saying "I feel [unhappy] because [I do not get to see you anymore and you spend a lot of time with your guitar]". It is best to be truthful with how you feel; not expressing your true feelings is an indicator of an unhealthy relationship. Show how you feel by labeling your emotions and describing when/how you feel this way.