Thank you all for your responses. I feel like part of my problem is that I've got my mom telling me I should "meet him halfway" and that "how will I ever know if he's trying if I don't give him a chance".
My counselor says that I have functioned for so long on the complacent (doormat) end of the spectrum that I should give myself a little grace in trying to find a balance. She feels like my outbursts are quite healthy for me in finding my voice, and that with time (like Barbara said) I will find that place of balance where I can be assertive without being aggressive, and no longer let people trample me before I finally completely blow.
Sillysquirrel....thanks for bringing up the cheating. I think my STBXAH did more damage in one night of infidelity (although certainly there must have been more) than he did in 21 years of drinking. No matter how much he grows through AA and therapy, I doubt that I can EVER have a level of trust with him that would allow me to be truly intimate.
It seems like just about the time I was starting to have some "normal" days after the loss of my dad, I am now faced with grieving the loss of my marriage.