Dog Heartworm Treatment

How would I be able to treat it? Sometimes, with low activity, she will start to pant. And one day, she didn’t eat at all.

i have two dogs and im pretty sure they both have it since they are always together… they have had all of the symptoms (diarhea, dull coat, little appetite, coughing) I really freak out when my dogs are sick so I want them dewormed immediately. Is it expensive? I know i need to supply stool samples but how much does all of this cost??
btw they have had symptoms for about a wk.

Before I go into it, I AM taking him to the vet TODAY, I already have my appointment but I would like some input as to what it might be:
My dog (a weimarener x) has been having extremely runny stool since Tuesday (at first I thought he just ate something he wasn’t supposed to), but since it’s gotten worse he’s lost his appetite and won’t drink very much either.
He is 9 months old, and the past two nights he’s been waking up to be outside and again his stool is extremely runny. He ALWAYS sleeps through the night and so getting up to go is unusual for him…Last night and this morning he has been shivering when he sleeps and that’s all he wants to do is sleep.
Also, he has started to not put pressure on his back right leg. I made him some rice/beef mixture an hour ago and he ate that fine and drank a few sips of water, I have also been giving him some ice cubes to try and hydrate him.
He is an indoor dog and is the only dog and is always on a leash when he is outside, he is also up to date on all of his shots, and was treated for worms when he was a puppy… so I have NO idea on what this could be!
Again I will be taking him to the vet TODAY just wanted some input, as i’m really worried about him…Thanks!