Is it fair or legal to stop me seeing my daughter?

hi well i was with my ex gf for just over a year we met on a dating site things were brillliant at 1st i took her 2 boys on as my own (there dads dont see them) and it was great i went on holiday already planned when i got back she told me solical servises were involed with her (child neglect) but i was determined to be with her so i stayed with her ... we got a house together and everything was going great s.s were coming out everyweek and we stuck together there was a incident when i grabbed her son and shouted at him and everything went wrong she wanted me out so i left and called her all sorts but i loved her and won her back promicing never to be like that again we had to have a interview with ss they told me they understand family life can be stressfull and that if i ever got like that again to get up and go cool down ... we got back together she got pregnant and things just got worse from that point the house was a tip she was moody i tried to talk to her about it but alls i got was " wat you having a go for" so in the end stopped trying to talk instead id critisize her about the house kids ectect then 1 day she kicked of big style telling me to get out when i would nt she went mentle hitting me jumping on me (kids were there watching and shes 7 month pregnant) and in end she phoned police i was shocked she could be like that ... we got back together but think it was wrong destion she was still moody (i know hormoanel) and i tried to explain to her that i thought its best we split but she did nt like that started saying stuff to wind me up and it worked i sent her loads of abusive texts and emails ...then anyway left her alone for few days then tried to get in contact about the kids and baby she ignored me and got police out on me arrassment charge so i never sent no more text emails ... she had the baby on sat 28th then her mam emailed my sister on the monday to tell us know she had her with a picture attached its been 4 days now since shes had her and shes still blanking me and the solicitors letters shes been sent .. what im asking is what have done so bad for her to keep my daughter away from