Having a dog has so many benefits and you clearly really want one. I would brainstorm a ton of scenarios that could throw a wrench in your dog's schedule/life and see if you can come up with a viable solution. For example...
Are you going to be heading off to clinicals alone?
Do you want to travel for away for them or go close to home where you have somewhere to stay that will definitely allow a dog?
Do you have a significant other or someone else who can help take care of the dog on long days? Is there any chance that person could be out of your life before/during school?
Do you have the savings or credit to take care of the dog if something bad happens?
Will you be able to handle it without ruining your performance at school?
What about when you graduate, will you be prepared to deal with the extra complications involved with moving with a dog?
What if you want to go on vacation during your off time, is there someone who will take care of it?
These are just some questions, I'm sure there are plenty more to ask yourself. I got a boston terrier puppy last October and then by January was set on going to PT school and so began 12 hour days between observation, full time work and school for prereqs. He needs to go outside ~6 times a day and goes to the dog park 2-3 times/week. He needs tons and tons of attention, time etc. I literally could not do it without my boyfriend who just works a normal full time job. And I would not have taken the dog if my boyfriend didn't have a wonderful, stable family who we know would take care of the dog if my boyfriend and I broke up, something happened to one of us, or we just needed a vacation! Same goes for if we break up, I'd be utterly heartbroken but I'd give him to my boyfriend and his family because he has those resources.
Anyways, that's my thought process going into PT school with a hyper, needy, nervous wreck of a dog
good luck with your decision!