How to deal with a dismissive avoidant boyfriend?

I think I'm down to the last straw here. My boyfriend is extremely dismissive, he constantly treats me with no respect and ignores me most of the time. He can't express his feelings, the only time he does is with a tantrum or anger. At the start of our relationship he was caring and kind. It's like his another person. I don't know how much more I can take 😭 we've been together on and off for 8 years. 
I don't know if I should try this anymore, I can't stop crying.