Married at 17 

It is hard to understand your situation because I am the nice/faithful guy getting left by my HS sweetheart (similar situation).  All I know is that, I am hurt by the infidelity, the lies she told me to carry on a secret life, and now by the loss of seeing my children everyday (worse for the children).  I know I didn't deserve to have my marriage go down like that especially when I would go to the ends of the earth to keep her happy (all the while she contributed less and less to the marriage).  I just wish she could of let go some other way without all of the humiliation and loss of trust.  She gave up on us just like that and I didn't see it coming because I thought she really loved me despite any problems we may have encountered.  I believed we loved so much we could work through anything. 

I believe odds are with each failed relationship the chances for divorce goes up.  Some people go from one relationship to the next only find out that they still haven't found the happiness they are looking for. (Maybe you will be one of the lucky few).  People want happiness in their life but they are not willing to work at a relationship to create that kind of happiness. It is no wonder why so many marriages fail, marriage is something you must work at.  I wish you the best in your search.:)