how to talk to you're partner without fighting ??

I feel eveeytime I try to talk to my partner it ends up in a fight...
I have strong opinions and so does he... we disagree with a lot... we don't like telling each other how to do things... I get upset easily and he doesn't understand why and then he gets mad at him for getting upset .. he walks away a lot during conversation... 
I don't know how to approach a serious conversation with him without him blowing up or without me blowing up... he and I say things that trigger us... we met when we both left terrible relationships...we both have scars...I dont know if we can make it through anymore... we have been together for 3 years now and I have left before because I couldn't do the fighting anymore and silent treatment.. I just want happiness all the time I feel like I don't remember what it feels like to be happy with someone anymore 
Help please any advice is helpful