Me (18F) and my boyfriend(18M) are having trouble communicating when upset

My boyfriend and I have trouble communicating when we get into arguments. We both tend to shut down and try to avoid the situation when we are upset at first we don’t tell each other why we are upset, and it’s stressful. We both tend to say “Whatever” or “I don’t care anymore” or “It doesn’t matter anymore”. We have banned the word “Whatever” since we use it a lot it worked for a while but then we started saying it again and completely forget that we had banned it.We tend to let our emotions get the best of us, and sometimes it leads to unnecessary things being said, we do end up solving the issue of why we are upset in the first place, but it tends to take many hours or the next day because we end up not talking to each other at all. We have been together for a few months and have had a past partner, I have been in toxic relationships, and he has had one other girl before me. I tend to become emotional when upset I tend to cry or become sad meanwhile he tends to have an attitude when upset, we are here to try to get some advice on what can help us communicate better.

TL;DR: me and my boyfriend want advice on how to communicate better when upset