My 2 Month Old's Diapers Have A Very Strong Sour

My 2 month old's diapers have a very strong sour smell.

She does not have a fever but is a little congested. She was restless last night and wanted to nurse just about every hour until she finally went to sleep around 2 am. Today she is back to her regular nursing schedule, but sleeping more often inbetween.

The smell started last night, but I thought it was just spit up milk. Gave her a bath today, but the smell is back. She is breastfeed. We are going in for her 2 month check up on Monday, but I don't know if I should take her sooner.....

We had an early thanksgiving with family on Saturday and found out my nice(1 year old) and nephew(3 week old) were sick. He had an upper respiratory infection and she has a cold. We are worried our baby caught something from them.