Injured at work, Losing full time status

[naydnd]

I was injured at work April of this year. After having fully recovered from the injury, I slightly reinjured my back and was placed on temporary light duty. My employer has changed my job duties while on light duty status and is requiring me to be at work at times that I am not available to work due to me not having a baby sitter those times. I am a full time employee and have worked for this company over 3 and a half years with this schedule. My employer told me that if i cannot be at work during those times that I am going to have to be switched to part time. Is there anything I can do to prevent this? I cannot afford to lose my job.