My kids had this exact virus last week. My son (2.5) started 2 weeks ago today -headache and slight fever. Had the fever until Wed. Very high at times (105.5 -in the ear, which is always a little higher than actual). No other symptoms other than extreme irritability and tummy ache. My 5 yr old daughter started on the following Tuesday. Same thing, high fever, tummy ache, no appetite and irritable. Took my son to Acute Kids (Someone already mentioned this -fantastic clinic in my opinion) on the Sunday afternoon and Dr. thought it could have been Strep throat or a UTI. Test was neg for Strep and I said no to the test for the UTI because I didn't think it was (he was peeing with no complaints).
We ended up taking my daughter to Acute kids the following Sat because she started to complain of a sore neck (just muscular from lying in bed for so many days) but they said many children had been in with this virus -very high fever for 4 - 5 days and just keep plenty of fluids in them. My kids both go to the same montessori school and I was told it was going around there.
Good luck, sounds like you might be towards the end, keep up with the fluids and cuddles. Also alternate between tylenol and motrin. I have also been told in the past that meds will only take a temp down 2 degrees. If your 6 mo old gets it I would def. bring him in to a dr. asap because of his age.