A.K.
Jennifer,
Diarrhea can go on for several weeks depending on the virus, I assume he is on no antibiotics? That will cause diarrhea. His he raw from the diarrhea? That would make him uncomfortable. Illnesses often disrupt sleep patterns as well. He is so young I think it is hard to know what to expect from him sleep wise. Some kids are better sleepers than others. I suspect he just isn't 100%. Could he have an ear infection? You said he did have congestion, ear infections will really wreck havoc on sleep!
Good luck!
A.