Feeling Depressed

I can't seem to tell if this is full blown depression or just that fact that I was watching a sad movie that had too many details about my own life. I have been feeling like a crappy mother today for even having a child. My husband has been diagnosed as having bi-polar disorder and I have had severe bouts of depression off and on my whole life. So I feel as though I have basically doomed my child to a lifetime of horrid things to deal with either with just my husband's health and my own and/or my son developing these terrible diseases. I know this is a fatalist attitude to have. The chances of him having these issues aren't terribly high. However, like I said, it has been a bad day. Writing it down does help though. My son is a beautiful healthy wonderful sweet 2 year old. He is full of life and yesterday when the screen door slammed shut on my ankle he asks "you o.k mama, you o.k.?, I kiss!" Like I said wonderful kid. But unfortunately it doesn't make me feel all that better to know that I may pass on these diseases to my child. I don't want my son to truly see the "crazy" side of my husband. Or to see either one of us so depressed that we don't get out of bed to have fun with him. The sad truth is that he will have to deal with those things. He is just so young. But he won't understand what is wrong till much later in his life and I don't want these things to destroy him. It feels as though we had him out of selfishness. But as terrible as I am feeling with all of this. My sweet boy is hungry and needs a diaper change. So I must go for now and finish my thoughts later. Till then I will hope for his future happiness and not losing his childhood too early.
Blessed Be.