It's OK to vent, and shows character on your part, to apologize to others here. I get that

That does make sense, that it could be the depression from the MS, as the main culprit. When I get into a depression, my body feels like crud more often than not. The more I feel terrible, the worse my mood. I have from a psychiatrist, depressive disorder, not otherwise specified. (Along with MS and anxiety state, unspecified--my exact dx from him, MS is left on my check up summary list)
Did other's in your life, suggest you were bi-polar, and how did your doctor come to prescribe the meds for bi-polar disorder? Was it over time, or something else. Mainly, curious, I don't want you to feel obligated to share, just thinking out loud. I'd had a handful of people in my life, through the years, suggest I could be. And I am not.
Sometimes, I'd express my anger in a frustrated, resentful way. As in, I'd let things slide and slide and slide, and anger would fester, and simmer, and build up, and poof...I'd snap back. So, to them, I'd seem, quiet and always pleasant, and they'd be taken aback because I dared raise my voice or express anger, and to them, that would seem moody and prone to an up and down outburst.
Honestly, I am more uni-polar. Which means, my mood is one way, but if I am angry, I seem angrier because I can have a rather flat mood.
It was a matter of working through things, learning how to deal with expressing my feelings on things, right there, right then. Instead of letting resentment build up.
It's just been a long process. But that's the gist of it. And why I ask.