My Soul Has Been Sliced Open, Bleeding Out, Help...

I 'm 27 years old living with my Mom and yes, we do live in a trailer park, it was not always this way though... Just over a year ago, I was out of town working for about 3 weeks.  While I was away, my Wife had an affair with my best friend and I mean best friend.  My Mom and his Mom grew up together so me and him grew up together from birth.  The thing that still is eating at my soul over a year later( yes, me and my still Wife are seperated and going through a divorce, hence I am living with my Mom till I get up on my feet) is that, right before I left I told him "This is the first time I've left her alone and you know her very well, would you please look after her for me while I'm gone and make sure shes ok for me?".  We also have a 2yr old son together and he is my absoulute world and for awhile there it felt somehow dirty to have a child with her, I don't know why...  I've since had numerous flings with women none of which lasted more than a few weeks if that and it still feels just as painful as it did over a year ago and now shes in a "committed relationship" with some dude which makes me feel HORRIBLE like what is the Mother of my son doing with this guy and is my son baring witness to all of this or does she have enough common sense to not bring him around him?  Theres so many unanswered questions and so much pain still, not to mention I've lost my job of 6yrs, jobless, broken, depressed and extremely lonely.  I happened onto this website and for the first time in over a year I have a little hope that there really is a light at the end of the tunnel...  If there is anyone out there that might be able to put this in perspective for me or even offer a couple of word of incouragement, it would be more than helpful as I feel as if I can no longer endure this pain...  Thank you for letting me share and if you have any questions or anything please let me know....