Definitely time to see your vet. Actually, your Dad was correct in his first aid measures. My vet recommends the same thing for the first 24 hours of gut issues. Beyond 24 hours, you need to consult your vet. I'm not certain about the "slimy" urine, but my best guess is that he's got a urinary tract infection that will need antibiotics. A UTI often causes incontintence as well. A supplement of concetrated cranberry juice like Cran Assure can help keep him more comfortable, but won't cure the infection. The cranberry juice keeps the products of the infection from sticking to the bladder and urethra walls, and keeps the pain down. Same thing that happens with humans. It really made a big difference in the comfort level of my dog who recently died of chronic kidney failure.
Get him to the vet ASAP,please