Very upset vent. feedback appreciated.

mtpgroove

So as a mom of a 5 year old kindergartener I am divorced and share custody. But my end is reversed. I only get to see my little on every other weekend an I am the one paying child a support. Long story short My lawyer backed out a day before the finalization of my divorce and I ended up going in unrepresented and lost everything including my baby girl. (I say this because people instantly think I am a bad mom because I don't have primary custody.) This is not true.

        So every moment I get with my daughter is important. So I volunteer at her school. I was supposed to be helping out today with the Christmas party and my daughter was  expecting me there. At 7pm she calls me frantic and crying saying "mommy why weren't you there!" It turns out the teacher changed the date and never notified me. I guess papers were sent home but of Corse her father never let me know. I try everything and go out of my way to see her more, help and be apart of everything I can and no matter how hard I try and what I do it never turns out right. The holidays are so hard I have a 6mo. old baby boy now and I want nothing more than all of us to be together for the holidays. Her dad is an evil cruel person who always makes me seem like I don't care and she needs to know we both love her. Please give me advice! what do I tell her?