Teen book about daughter with agoraphobic mother

This is a vague memory of the plot of a book I read in middle school or early high school. The main character is a daughter whose mom is agoraphobic and moderately mentally disabled. I believe the mom at one point was not agoraphobic and she could still navigate familiar areas by herself despite her disability. I think she was also at some center in her younger life where she met a similar man and she accidentally got pregnant, the baby daughter being the main character. Something happens to the mom and the daughter decides to travel by herself across states to find her dad(?) moms friend(?), I can’t remember exactly who she’s looking for but she goes on the journey and eventually finds the person I think. She doesn’t get the answer she wants and ends up going back to her mom. I think something else happens and the ending was somewhat happy. The daughter is also lucky and can guess how many pieces of anything are in a jar to the exact number (this somehow becomes an important part later in her journey but can’t remember the details of how). These are the only details I can remember, does this sound familiar to anyone?