So my dog Odin has been having some coughing/hacking fits lately, and I'm not sure if he's getting sick, or if maybe his constant pulling is becoming a problem. He's a pretty high energy dog (sheltie/border collie mix) and I take every opportunity I can to take him out to the local dog park and tire him out, so he spends a good bit of time around other dogs. When he isn't at the dog park he gets walked around my apartment complex where there are lots of squirrels, cats, and dogs that he isn't allowed to play with (The dog owners in my complex are weird that way) and he's constantly pulling at his leash to try to go closer. I'm not sure if this hacking and coughing he's been doing lately is a sign of kennel cough or some other sickness or if he's just strangling himself trying to run after things. His collar is pretty loose fitting and I can easily get almost my whole hand in it while he's wearing it, so I know it's not on him too tightly. I'll probably pick him up a harness in case that's the problem, but I'm still worried it could be something more severe.

He has been pretty slow/lethargic when at home, but I don't know if this is sickness related or because I take him to the park for about an hour at a time every day I can to work out any energy he has. He's not slow or lethargic at all while we're out. He's going to the vet on Monday for a checkup, so I can ask there, but I would like some opinions before I go since this vet likes to charge a lot of money whenever I bring up a problem. This may be the last time I go to this vets office with him, since I'm really tired of paying the monthly fee (We're using Banfield right now, shopping for others).