heartroken and pregnant!!

Am new to this bt could realy do with someone who undastands and someone a can talk 2......in september my partner of 9 years left me pregnant and our 6 year old daughter for someone at work!! Hes is stil around alot and helps me and always sees our daughter and says he will always b there bt the lonliness is worse thn ever and the tears the last week have been none stop!! A honestly dny kno were 2 go from here how can sum1 give up on their family so easy without a fight bt still really care!! The thought of him happy living the life of luxary with her as he moved in within weeks and seeing her kids daily is killing me as a kno he misses waking up with his own daughter daily as he is pushing for me 2 let her meet her already bt my daughter is already struggling with this cgange and think she is nowere near ready.....a cant let go and always hoping its jst a rebound n wont last even if he dont wana be with me as a dnt believe they deserve 2 b happy....selfish of me maybe bt they have ruined my life...any advice much appreciated x