i caught my man with another girl??? sorry if this seems long..?

but i need to get it out of my chest, on saturday 19th may 2012 it was my boyfriend's niece birthday she turn 14 years old and she throw a party at her parent's house and invited all her friends that went to school with her, my boyfriend is 25 years old and i have a 21months old boy with him, i'm 24... the mother of his niece told me that it's best if i don't come to the party because there would be lots of school girl there and as they know how my boyfriend are (womanizer) they didn't want any problem form me being mad or jealous, so i didn't go , but my boyfriend went there with our son and his mum... i was at his place alone then my mum call me and tell me that if i'm not doing anything go with them at a night fare i agreed and get myself ready... i try to call my boyfriend to tell him that i'm going with my mum i couldn't reach him, i texted him on my mum's phone... later that night he called me nad ask me where i was and started swearing at me and telling that i should have call him not text and hang the phone in my face, when the night fare was almost over my boyfriend called me several times but i did not pick up, it's like something told me not to... i went to his place and try opening the door it was lock from the inside with the key still on it so i could not use my key, i went around the house to get him to open the door when i open the window curtain i found him in bed with a girl both naked, the girl didn't even saw me seems like she was drunk, he didn't recognize it was me at first then when he look closer and saw me he close the window in my face and turn off the light, ashamed.. i went back to the front door and knock on his mum's door she opened it and when her mum open the living room door he was trying to make the girl escape but did not have time so he brought the girl back to his room and lock the door keeping the key with him, his mum didn't saw her because she was behind me, i was so mad and hurt and he was pushing me away telling me that i'm lying there are no one in his room and that i did not let him know where i was, he told me he don't need me and get out of his house, his brother was sleeping in the other room came out and he turn against me and giving his brother reason, my boyfriend treat me like dirt or a dog, trying to kick me out the house, dragging me out but i re-enter because my son was in that room and i told him to give him to me and he hit me in my face just because i saw him, that girl took out the window in his bedroom and run away, can you believe that while he was with someone else my son was in that room in his crib sleeping, i did' go away immediately because i told him to just give me my son and my stuff so i can go, he open the door when that girl already left i went in there get my boy and wait for my step-father to pick me up and i went to my mother... the next day i went there and take the rest of my stuff he was there sit on the bed and just look.. his mum was so devastated because i was her helping hand at the house and we got along well, she cried when i got in the car and left.. but what makes me happy is that i always knew he was cheating on me with so many girls and i forgave him so many times before, but i always told him i will see him in my own two eyes one day and this will be the day i move away from him forever, that day God bless me not to answer my phone and i went there unexpectedly, and i finally got the courage to leave his sorry a** that girl he was with is a 14 year old girl, from his niece party and his brother is a grown married man and he was with one too in the other room cheating on his wife.. that's why he defended his brother... but since that day until now i never cry one single tears it shocked me because i really loved that guy truly and things were great but i don't let this get to me, my family is my straight especially my son, i don't feel sorry for him not to grow with a dad and mum, i feel sorry that this is the father of my son and i wish he never treat a woman like that... God will bless me and he will someday realized what he have lost... do you gy think i did the right thing...any words of encouragement and advice is very much appreciated.. thank you!!!