Screaming in the car is good. Though it's best if you wait until you are in there on your own...I won't let anyone visit me in hospital anymore. This has upset a few people, but it's not about them.
Learning to deal with the well meaning is one of the hardest lessons cancer has for you. I see a shrink periodically when I find I am falling off the edge, it helps. It also helps to tell people you hate it and you don't want to talk about it. If they get the shits or become all horrified, they aren't the people you need around you at the moment.
The mastectomy thing is horrible and it's difficult to imagine there will ever be any sort of normal again. I think of recovery a bit like cleaning up after a wild party--you are in the middle of all this mess, most of which you didn't make and you are now responsible for a sorting it out and getting rid of a heap of garbage.
Figuring out where to start is daunting, then you get a bit of a plan, then you get a couple of clear surfaces... I'm usually guilty of going at it too hard and wanting everything fixed too quickly. I generally make a few monumental cock ups, but I was like that before BC so it really is situation normal.
Find way that you can cuddle your kids without everyone yelping, things will follow from there. Marg