I feel like i am not happy but i dont want to leave him?

i have been in a relationship for over a year and a half. i am 19 and he is 24. i rarely see him at the most once a week but lately it has been once every two weeks. i always have to ask to go out because he never will. i feel like sometimes he doesnt want to see me, and he snaps and is mean when i ask him whats wrong? or how was his day? his answer is that he is stressed and i dont understand that he has so much going on. well, i dont understand because he doesnt include me in his life. im his last priority if he had a dog he would put the dog before me. he cancels on me 90% percent of the time, and today i wanted to have a picnic and sit watching the view of irvine over this mountain so i asked if he was free today (so i wouldnt make all the food for nothing) and he also said he was going to see me today but of course he cancels and gets mad saying that i know very well how much house work and bills and laundry he has to do this weekend. i would offer to help him but i feel like i wouldnt be invited over. i cant get the strength to leave him, but i am not happy at all. he never has gone out of his way to do anything for me and i have to wait around until he wants to see me because it can never be my decision. i cant talk to him also. i have tried and it goes nowhere