I need to cool down

What do you do when you feel the urge to blow up at your significant other? I was sitting on the couch feeding my 8 month old her bottle and taking in the baby snuggles, my boyfriend was sitting on the other couch staring at his phone and my8 year old was asking for supper. Well instead of getting up and heating it up for him my boyfriend says “put the baby down and get your son his supper, he’s hungry” then goes back to staring at his phone. Put your fucking phone down and get off your ass and you get it! Ughhhh I hate conflict so I hold all my anger in but I literally just went in the bathroom and gave him the middle finger through the door while swearing like crazy in my head 😂. I always feel like I’m going to blow up when he does shit like this. But I hate fighting so I never confront him. I just hope that he will realize what a dick head he’s being.