pepper, I just read the posts you had posted before, it was very touching. I lost my first pet ever Sandy to the kidney failure last July, I was heartbroken.
And in Nov, I adopted Zack and just like you I had to went through the heartworm treatment with him.
But the good news is, they will get much better. Zack was very quiet and calm when I first got him, now he is heartworm free, he is sooooo much hyper than before. So just wait to see, LD will be even happier 5 weeks from now.
Zack had his first 2 treatments (kill the audlt worms) about 6 weeks ago, and 2 weeks ago went back for another 1 (kill the baby worms, this was much easier on them than the first 2). Yesterday we went to vet for a check up. Most pets are heartworm free after the treatment. then they will start to have the heartworm prevention pills.
Big hugs to LD and you