How do I just let go?!?

my Story starts on July 21st 1991 I meet this man when i was only 13 yrs old he was 20 oppsss my bad lol we feel so in love had 3 beautiful baby's together Sonja in 95 richie in 97 and our baby eddie in 98. by that time I had reached the age of 21 and was a the most selfish point in my life. I think from starting this relationship at such a young age I felt as I missed out on something.... Witch in the end was nothing... I cheated in 98 by 2000 I left my long time love marcos well it was a on and off again thing.. See now let me give u some insite on Marcos. He hated drugs or anyone that had anything to do with them. He was not into gangs he was just a normal man trying to do the best he could for his family. He adored his family and friends to no end... but when i finally left for the last time he could not take life feel in such a bad depression I left him for a gang memeber so I think he felt he has to fit that role to get me back he would begg and beg for me to come back to him.. I just did not see what I had.. he got on meth he said it helped him with his pain... he started hanging out with the wrong crowd and dec 20th of 2001 he was murderd the worst day of my life....I guess in the time i was in and out of his life he found a girl named kelli i had no idea about kelli till his awake... what a supprise for me and she was prego with his child =( Now I have lived with this guilt that all this could have went a tottaly diffrent way if only i was not so selfish if i only would have stayed with my family. now 9 yrs later im remarried and it has tought me a huge life lesson to not take anyone for granted I hate ppl in gangs now my 3 babys hurt day in and day out for their dad. I miss him every sigle day of my life I did how ever write him a letter telling him I was ready to come back that letter did not get to his house till dec 21st just 1 day to late... how do you deal with such a horrable thing I cant do this i hurt so bad I want to forget everything about him.... Kelli's son Anthony (marcos son my kids brother) got taken by cps with along with her other 2 kids we all went to see anthony 2 weeks ago this is the first time i have seen Kelli since the baby was born may 1 2002. She was telling me about a letter marcos had wrote her saying how he hoped she would be happy raising a basterd child and that he was going to die be for christmas. So he knew now all my guilt ya i still hold it but now anger has come into my heart. maybe my selfish ways are coming out again idk but im like how could he have done this to us... was life really that bad didnt his children keep him going didnt he love them enough or me. Everyone says he loved me till the end and never gave up but I feel he did and I dont even know what to do with my self im going crazy I need help plz help me someone anyone..........