Different types of thermometers are going to give you different readings. You need to use the same kind consistently and know what is normal for you. Also take your temp several times and then average the results. We get a slightly different reading each time, even within a few minutes.
Going down a degree from the time your temp was taken at the appointment until the time you took your own is not impossible nor unreasonable. I think most people fluctuate by at least a couple of degrees all day long.
DS '04 "Boogaboo"
DD '08 "Lilybear"