Thank you guys so much for your concern. Marty has been feeling fine since this morning. He's been normal and playful and hasn't had anymore problems. I called the vet again right before I was supposed to go in and they said that since he was still doing so well, I didn't need to bring him in. (It would've been pushing it to make it back to class on time...where I am now so that was a relief.) They said to just keep an eye on him and if he gets sick again, to bring him in immediately. I'm so glad to have my puppy back to his normal, playful self!!
Again, thanks so much for caring.