Confused needs girly advice please

So here it goes.. me an my So have been together for 18months now, we have had alot of ups an downs in a short space of time.. yesterday I saw a text on his phone saying 'don't block this number as **** won't be able to get in touch with you an this is her only way' so i was like okay who the hell is she..?! He made a story up saying she was calling for something else to witch I didn't believe, so I said give me her number he didn't want to he was shaking an could see he looked worried. I got the number an i told him I was messaging her to find out who she was an what she wanted, so I messaged her saying I was him an then he blurted out how he was pissed of with me last week for breaking his car window an thought he would get me back by planning on meeting this woman. I still messages the woman an she wanted to me him so I went along with it an ordered her a taxi an told him that we would find out the truth face to face with her even though she didnt kno that I would be there.. he said I've told you everything you're taking it to far I didn't think I was an couldn't stop laughing at him, I had a message saying she was on her way in the taxi an he didn't like that so he asked me if he could have a cigarette an i said there in the living room after a couple of mins I went to get one to find out my front door is open he has only ran off.. I went looking for him an could not find him anywhere then I called his mom an she said he's on his way to her at her boyfriend's place so I said get him to call me when he's with you but I thought fuck it I'll catch him now an went there his face when he saw me was a picture. He asked me of id seen her I said no bcoz I went looking for you, I said its okay bcoz I will get her here when youleast expect it an then he told me he was going to get a cigarette of his mom to my horror again he legged it out the window an ran again I was like are you taking the piss.. so I left there an on my way back home I had a call of his mother an she asked how i was an that i then asked her if he came back she said no she then asked me if i was home an i said no not yet an told her I wouldn't be staying as I'm leaving to stay with family (I live far from my family, I moved here bcoz of him) an then I heard her say you better talk to her now an he said no I can't she then said talk to her or get out, then he spoke to me an told me to read my text on my other phone I couldn't cuz my phone was dead as to what he said explains everything I need to know. So I get home charge my phone read what he's put (previously when we got together he told alot of people lies about me so I told him it was over an ended up going to dinner with my friends male friend) to me I thought you are taking the piss now as he said he done it to get back at me, I was like i was dating you for 3months I barely knew you an after what you done to me in the first place you're lucky I came back!! What makes me mad is that we had a baby together but the baby died while pregnant an i thought we was stronger than ever but really we wasn't.. he told me he don't see that we are over an I'm over reacting an its all one sided.. ladies am I over reacting or doing the right thing by leaving.. he said he hadn't met her an that it was only messages but she's an ex of his