M.S.
I went thru this with my daughter.
What i did was we went to wal-mart and i asked her "what toy do you like the most here" she showed me and i bought it and when i bought it i told her that if she would go #2 in the potty 7 times in a row that i would give it to her.
she was so happy, she worked real hard but she made a mistake one time. I told her that she was doing a great job and that i was so proud of her, but mommy needs it to be 7 times in a row. She tried again and she did it and she got the toy that she wanted.
that worked for us. It might work for you.
dont give up it takes time.
Mrs. S