Don't worry about it! I think that you are being strong to deal with your own BP and your son's. Maybe sometimes you are being too strong? It's okay every once in awhile to give in and want somebody else to be strong for you, you can't do it all on your own. About watching the movie that sort of pushed you over the edge, I have a few suggestions that may help or may just sound silly. I am 24, and I know that I'm not a kid anymore, but sometimes doing things that remind me of that happy carefree time make me feel a whole lot better and pull me out of that depression slump. (Sorry if it sounds silly) but I like to watch some of my favorite Disney movies, or cartoons, anything that is happy and doesn't make you worry or think about what's sad in this world. I like to draw or paint, and yes, I'll admit it, I still like to color every once in awhile! I know, it may sound weird, but it is what makes me happy and releases stress and sadness too. You may have things like this that you can do. Watch a HAPPY movie, don't give in to the need to see something sad, don't give in to the need to listen to sad music or engage in sad/depressing conversation topics, etc.
Also, don't worry about leaving the health profession! From the sound of it you have helped a lot of suffering people, it's your time to be helped now. Maybe in a small weird way it is better for you too because you won't be around people who are also suffering and making you think of your own suffering.
I hope that you start to feel better soon. Write back if you feel you need to or want to.