Hi I Have A Daughter She Is 7 Years Old.

Hi I have a daughter she is 7 years old. Resently she is getting abdominal and hip pain. So I went to the doctor they said just give pain relief syrup she should get better. But she still gets it sometimes like 1 2 time in a day she will complain and I will give her the syrup. But I have noticed since yesterday when she burps it smells of bad egg smell even though she hasn't had eggs for over a week now. Can you please explain

Thank you