99.9 is not very significant, just low grade, usually 100.4 or higher is consideredas more significant, but the wheezing, especially in a 3 month old, is definitely something that needs to be checked out ASAP. It may not be RSV, but there are a ton of other viruses that can cause bronchiolitis, which seems to be what your baby has. If the wheezing is significant, he will probably need to get a nebulizer to get breathing treatments at home. NEVER stop feeding your infant because of fever, they actually need more fluids because fever makes them loose fluids. The only time I would stop feeding formula is if your baby is throwing up everything you feed him, in that case you give a trial with pedialyte and get to a doctor ASAP as well.Good luck.