I am so sorry for the loss of your husband and the surrounding lack of support. It is truly an awful and isolating feeling to be left alone with pain that big.
I am also sorry to hear about your friend.
As for reliving things, it makes sense that painful things will come back up and be thrown into the mix while other painful emotions are happening. Have you ever, in the past, been able to tell anyone about what happened that you are currently reliving?
In my experience, letting go of memories and the feelings unfortunately means speaking about them, processing them with support. I don't think the ever truly leave us but over time the rawness becomes a little more hardened, like a healing wound, if that makes sense.
If you struggle to tell someone what happened and you freeze, do you think maybe you could write it down and pass it on to a trusted person or medical professional? I've found that that way I know it's at least out there and I can't take it back and it's been done.
I wish I had more useful advice to give, but instead I will say that I am sorry you feel so alone with all of this. We see you and hear you here and acknowledge your pain.
Best wishes to you.