Why is he being such a jerk?

My bf and I have been in an on again off again relationship...with this on again relationship that start back up over a year ago...I had moved to other state for a better paying job and would go home to see him maybe once a month or every other month because I have one full time job and two part time jobs. so it was hard to get home often..he would never come see me..his excuse was because he do not have a good vehicle and that he work all the time...so I drove the 4 hr to see him...He also insisted on being a friend with me on facebook...but when guy friends would comment on my pictures he would think I was sleeping with them or chatting with them...anyway he broke up with me...and I agreed it was for the best...now he's being a complete jerk...leaving nasty comments under my fb photos and leaving nasty tex messages...I had to blocked everything so he couldn't har me anymore...but why such a harsh reaction? I tried the communicate so maybe we could work things out or at least be friends but he didn't want to resolve anything just argue and complain...then when I left it alone that only made him more angry...Is he mad cause I am not upset over the break up? Why is he being a jerk if he's the one that called the relationship off?