Im really worried about my beagle...please help?

my beagle is only 4 years old now and we just got a turtle ...he watches it like a dog..and is very intreged by it im not sure if my dog has salmanilla or something that a previous dog died of or something else. I plan on taking him to the vet on monday sicne they are not open today but since so often i have the vets saying they dont know what is wrong with my animals and still charge and arm and a leg i figured i would ask yahoo what they may think is wrong with him. SO basically i know turtles carry salmanilla and havent noticed my beagle licking or digesting anything around the turtle tank we have outside,i havent noticed him throwing up, but he did have a sezure type shaking for about 10 minutes last week(which really scares me because a dog i had recently die had the same thing and the vet never figured out why exactly), today he is not interested in any food or water except for dog treats which is very unusual,he seems ill or as though something is off and isnt his perky usual self, i noticed his back legs almost trmebling and i picked him up very gently to place him on the bed so he would relax and sleep and he yelped i picked him up gently like i said and it was around his upper body so this is also almost seeming like the dog i recently had die...that dog was told to die from his teeth which caused an enlarged heart and a blood clot...we plan on getting the beagles teeth prffessionally cleaned for the 1st time in about a month....what do you think is wrong? is there any way to help him now? is its from his teeth (which dont really look bad just have some tarter buildup from what i can tell) then can a cleaning fix the issue or something else? if its an enlarged heart can the damage be reversed in any way? PLEASE PLEASE PLEASE HELP THANKS