My 7 year old dog recently had his first seizure, Could this lead to more seizures and shortness of breath?

He had a seizure 3 days ago. Now today he had another. Ever since the first he has had a very hard time breathing. He is a 7 year old bull mastiff and isn't overweight and has had no problems like this except a thyroid problem. He is going to the vet tomorrow I really hope they don't have to put him down.