confused by him

lately my boyfriend and i have not been seeing eye to eye. we have been arguing all the time and its just tiring now. im starting to worry that we are not going to work out and the thought of that hurts. i do care about him, i do love him, i want to be with him. we been together for a year now and the entire time it was great up until this month (april).. .everything was fine. being long distance was never an issue but now i am starting to think it is. part of me thinks its his insecurities kicking in and then the other part of me thinks it is more. i mean we have always been open and honest with one another and then he just all of a sudden shut me out. we dont talk like we used to and when we do speak we are always arguing. he has accused me of cheating and i kind of laughed it off and after that he just kind of shutdown. i dont know what to do anymore. i dont know what to say. two weeks ago he called me accusing me of cheating and then we didnt speak for a while and then out of the blue he calls me earlier this week (monday) asking what were OUR plans for the summer. he was talking about how he misses me, cant wait to see me, he cares about me, we are going to do this and that together and we are going to have fun....he was himself again. he was the man that i fell for. but then that lasted only one day... that day, by tuesday he was back to the mean guy. I AM SOO CONFUSED. i dont know what to do. i have been struggling with the decision of staying with him and making it work or leaving. i know its only been a month that its been like this compared to twelve months of good times but this month has hurt me. i guess things hurt more when you really care but i never thought that i could feel so bad with him. i mean he introduced me to his mother as her future daughter in law. i have met his entire family, so what is the problem?
what do you all think i should do? should i stay, spend the summer with him and see if things go back to normal? or should i just end it now?