left with my daughter now with new man

i thought our marriage was pretty solid, then nov th she asked me to leave saying she was not sure if she loved me. i left for a few days in shock she moved out with my daughter to her parents. since then she has blamed me for her depression made some terrible exagerations to her family and friends who now hate me, made it difficult initially to see our daughter. just two and a half months later she is with an old boyfriend who spends time with her and my daughter, then two months later moves in to her parents, they are in love and are going to get married! She is horrible to me!! I did everything she asked, gave up weed, saw a councellor, but i would like to say that i was a very attentive and responcible husbabd and father who did almost everything for a long time as my wife had post natal depression. my daughter is 3 now, this is just the basics! any insights anybody?