Dont wait 7 days!
Push the pedalyte and take him to his ped and have him tested. They will test the "messy" diaper. So if nothing else take a poopy diaper in with you just in case he doesn't have a messy one while there.
My son was fussy but still acted the same, just a little slower... you could tell he didn't feel good. I took him to the Dr and they told me that it was just the flu. I explained this has been going on for 3 days and he isn't getting better. They were going to send him home and write it off as the flu. I got mad and told them they need to do more than take his temp ( it was normal, he never had a fever) and weigh him. Well they wouldn't and sent him home.
2 days later I went back with him and again they were going to write it off as a bad case of the flu. I demanded they do something else. I actually got into a yelling match with the Dr. I made them call in his regular ped ( she was out both times we went) and I wanted her to look at him. After a half hour of going back and forth they called her in. She took one look at him and was honestly pissed they were going to send him home. She had him tested for the rotavirus and it came back positive. In the mean time she hooked him up to an IV because he was so dehydrated. I felt horrible I didn't realize he was dehydrated.
I thank God every day for my bullheadedness and demanded more for my son. After she admitted my son to the hospital she came up that afternoon and said had I went home with Devyn he wouldn't have made it to the morning. He was 80% dehydrated and his kidneys were actually starting to shut down on him. In the two days between seeing Dr's he lost 7lbs. He had an endless cup of water and drank it.. I was always refilling it. It was just coming out of him faster than his body was absorbing it. Plus it didn't have the electrolites in it that he needed.
Just be careful with this virus... it scares me when I hear of kids getting it after our experience with it!