Still in love with my ex it physically hurts to see him with another girl?

I was with my ex for 1 year and in the beginning things were absolutely amazing, couldn't of asked for a better partner he was my best friend, then around 10 months into the relationship things became weird between us but none of us made it obvious, we would just argue about pointless things and push eachother away. We split up for the first time a little while later but managed to talk things through within a week we were back together, but even though we were together the weirdness was still there, We were both paying eachother less attention and things got bad between us again to the point where we couldnt trust eachother anymore.. I thought he was seeing other girls so i made a fake facebook profile to catch him out and i was right, he agreed to meet this fake profile girl for sex.. he then found out it was me and split with me (even though he was the cheater) and we split for good. When we split i was soo confused i became psycho, hacked his facebook read his emails and texts and chucked abuse at every girl that spoke to him, he loved it. He loved knowing i wanted him back so bad and i could never have him which made me hate loving him more and more. The psycho behavior happened for about a month until he went abroad for 3 months i had no contact with him at all. I found myself a new bf and liked him so much i didnt even think about my ex - until my ex came back from being abroad. As soon as i heard he was back so much emotion hit me, i rang and text him everyday telling him i loved him and i wanted him back, even though i has another boyfriend. My ex agreed to meet me and we slept together a few times from then on we started seeing eachother again, i was so happy, i dumped my boyfriend of the time and hoped for the best with me and my ex. But then like old times we had a massive arguement again and getting back together went out the window, so now i am back to stage one feeling lonely, heartbroken, depressed and acting like a psycho when he talks to other girls etc. To make things worse i have just found out im pregnant and the father could either be my ex or the lad i was with for a few weeks :/ Being pregnant is definately making me feel a lot more emotional about still loving and missing my ex i am still being a psycho ex-girlfriend and i kno he will never have me back so i just want to make his life hell all the time.. i wreck his relationships with females and cause him stress but he still always tells me he wants to be friends!! That upsets me because i want to be more than friends, so i do things that make us argue even more! Feel like im going in a circle i just want to get over him :( And he has a new girlfriend who i know he really really likes and i just want to mess it all up for him.. he has taken her to a ball this month (the same one he took me to when we were together) and it makes my heart psychically hurt every time i see the pictures of them together.. Although ive had advice from friends i would really appreciate some from people who are not biased.. Any advice is much appreciated btw thankyou.