why they cheat?

by my
(saudi)

ive been in 4years and 4months relationship. i know in normal realtionship its normal to have misunderstandings. i always accept and forgive him for evrything. at first im hesitate to trust him but since i already learned to love himi trusted him..when we were in 2years of being together i had an oppurtunity to go abroad for work..i decided to go because i have a lot of plans for my family and for us..i want to help my family as early as posiible so that if the time comes that i want to settle down with him there will be no problem. so the long distance relationship started..before i leave he have a lot of do's and dont's for the two of us.we have a lot of promises for each other. in the first year of being apart everything was ok but we cannot avoid some misunderstanding because of the differences in our time but we trying to work for it and we survived...as time goes by i started to think something about him..i think that he is not loyal to me anymore..i always confronted him every now and then but he keeps on telling me to trust him..inspite of all my doubts i chose to trust him..

im a kind of person who always thinks the worst scenario because i want always to be ready for everything. i believe that if you think of that such thing and if it will happen, the pain can be lessened and if not happen then, great, you can be happy.

after my work..his yahoo account was always open in my ipad and one notification appeared 2 hours ago.. someone posted in his timelime "kmusta n baby mo?ok n b?kelan uwe nyo?". goose-bump.. what the hell is this.. i tried to view his timeline but its shows cannot be viewed or may be deleted..
i contacted him right away..i ask him to be honest to me. at first he denied everything. i tried to believed him but it always bothered me..you know the woman's instinct..i always ask him..after two days of thinking about it i told him that it will be the last time i will ask him and if he will not tell me i will try to ask someone and he becomes speechless. i started to cry and i already heard him crying too. then finally he voice out, can you still accept me?if you loved me you will accept me and gave another chance. ive committed mistake, i was wrong, im suffering from it for a long time. i had baby from a girl i didnt love. his 1week old already."

hoo..i thought i was prepared for a scenario like this but why i feel that i want to die..i dont know what to say..i cant imagine that i will be hurt like that. everything flashed back on my memory. now i know why we always fight..i should believe my insticnt not for what he says..

i dont know what to do..i love him so much..he is asking for my forgiveness..i know i should leave him but why i cannot do it..

LORDGOD, please help me to be strong, please help me to find the right decision for me..