Well our Fats has been doing better. The vet said Fatboy doesn't tolerate cephalexin well (my husband and I figured this much out). He also said the effects he experienced were similar to taking too many shots of tequila. This is where the throwing up and being too loopy to stand up came from. His medical file now says no more cephalexin. Fatboy is on amoxicillin and has had no bad reactions so far.
Thanks for everyone's input! Fatboy is doing much better and is back to begging for cheese and doggy treats. This is always a good sign :)
Fatboy aka Stinky :)