Hello, Here I Am.
I have always had a problem expressing my feelings to other people. And when I am angry and upset I tend to "let it all out" because I keep things in for so long and explode. Obviously, this is not a good thing and tends to get me in trouble as this is not appropriate. Thus, sometimes I take out a diary and freewrite --I let all my feelings out. I write everything I feel and would love to say and this way I can get my anger out of me and then put it down on paper. I used to have a therapist that would say take it from here (my heart) and put it there (the paper). By doing this I really get all the issues out and then I am able to say this constructively and appropriately to whomever I am dealing with. Or, if I feel that I still cannot do that, I write a letter that appropriately explains my feelings and states how I would like things to change.
Since starting this practice I have considerably cut down on my meltdowns. I'm still not perfect but I find this way is more effective and appropriate for me. Perhaps you could consider this route for yourself as well?
Good Luck. You sound like a caring person and just need to find a good way to get your own points across.