Shocked

Hi I was going out with my boyfriend for a year I thought everything was perfect until he started his new job the moment he got it he changed completely started being distant bought new clothes new perfume never had time for me did overtimes the moment he started his job he invited girl from work on fb I know its only fb but my gut feeling was shouting at me for the 3 months he was at that job I even confronted him about it many times it led to us breaking up because I was putting 100 % into the relationship it was long distance as well I would come on the weekends but always complained how tired he is he even started taking overtimes at his work and work on Saturdays I broke up with him thinking it was my fault for accusing him of cheating with the girl at work but 2 days after we broke up one of my old friends from his town called me that she has seen them over course of 3 months so when he started his job.after the break up and before I knew he was cheating I even blamed myself now I'm in a situation where I feel completely betrayed and I cant believe how someone could lie to me and lead me on even after confrontation and head wrecking he knew that i knew how can someone to that to any human being i just dint understand i don't even know if i will ever be able to get into another relationship and tbh I'm not even thinking about it i just feel physically sick from everything it got to the point before the break up where he was telling me i was a psycho that i became cold that i was distant and it turned out he cheated why on earth would a man not tell to someone that they met someone new is it that hard ? i just don't get relationships anymore. any tips on how to cope and even in the further future how to date because I'm at the point now where i think ill just spend time on my own because that just mindfucked me to the highest of my nerve point.I cared about him a lot always gave him space never texted too much never had problems with him going out i would even clean his roomand i never tried to be his mother ofcourse but i don't get it i never even expected him to pay for anything i just wanted him and us to he happy and enjoy life i don't know what i did wrong that led him onto this. i know some couples go through rough times but if they both want to they can work it out why didn't he... i really loved this guy and i never forced anything i even told him if he is interested in another girl to tell me and we will part our ways like mature adults would i don't understand why he couldn't not tell me even when i knew