Potty Time

So we are potty training or least trying. my daughters will not use the potty for me. They go for daddy, grandma, the babysitter, everyone but me. We have a reward system where they get a sticker to put on their potty chart. Today when the girls woke up I asked them if they wanted to earn a sticker and go potty and they both yelled "no" at me. 3 minutes later Maddie sits on the potty for mike. they follow me into the bathroom and when they hear me pee they say, "good girl, momma" "you get a sticker" "your a big girl". yet they refuse to go potty for me. I feel like I am failing at this part of motherhood. they are with me more than anyone but they wont go. I don't want to force them because I don't want going to be a bad thing or something they don't like to do. what do i do?