Oh, yeah, I know how it feels to be marginalized at work. It sucks.
Have you thought about looking into therapy to help build up your confidence and assertiveness?
Try not to catastrophic things. SOMETIMES shakeups at work, as stressful as they are, can make us look at whether it's time to move on to a new opportunity elsewhere. I'm not saying that's NECESSARILY the answer, just that you don't know how things might eventually shake out. I'm a big believer that sometimes I need a good hard shove from the universe to tell me I need to be doing something different.