My kid doesn't want to live with me

My ex dumped me when our daughter was 18 months old. We split, and I took our daughter to live with my parents 2 states away. My ex pursued custody and after several months of court battles, we reached an agreement. We have 50/50 legal and 65/35 physical custody orders in place. I have the larger share of physical custody.Our daughter is now 6 and ever since she was 2 years old, she's been inconsolable when coming back from her dad's. She clings to him and begs him not to leave her with me. She never cries so hard in any other situation. It doesn't matter what activities I plan for her or how I hype up her return, she cries in her room for hours and mopes for a couple of days after coming back. She talks constantly about missing her dad. Also, she's always really excited to see her dad every time he has parenting time. She runs away from me to him laughing and smiling. He always has to remind her to give me goodbye hugs and kisses. It hurts really bad because she has never been that excited to see me in her life, not even as infant.To make matters worse, my ex started dating a woman soon after we split up. He just married her last month, so she's now my daughter's stepmom. My daughter adores her. She has her own special name (Steppy) that my daughter picked for her, and from what I hear, she can do no wrong.Everytime I have to discipline my daughter, she says she wants to live at dad's house. Hell, she will randomly tell me she wants to live with her dad on a day-to-day basis.I messed up the last time her dad had weekend visitation by asking her why she doesn't miss me. She just cried harder and now doesnt want to even cuddle with me. It's not the first time I've let my insecurities get the better of me, but its hard keeping my mouth shut when it hurts so bad.I'm not a bad mom. She's healthy and usually happy baring the transitions with her dad. Idk what to do, and at this point, I'm almost willing to give up some custody to make her happy. I just want to be loved as much as she loves her dad. After 4 years of being the parent she doesn't want to see, I feel pretty crummy.Advice? via /r/Parenting http://bit.ly/2DjWivJ