Dog died after having diarrhea.

My dog Dott is a small Aussie mix, weighing about 28 lbs. She is normally very energetic, playful and adventurous. I began noticing that she was not being herself, still playful, but spending most of her time under my bed and not wanting to go outside. She loved to eat, was obsessed with food and that had not changed. I thought maybe she was in heat because she would get that way during that time. The other night I awoke to a horrible smell in my room. Dott, who in her 9 years never had accidents in the house had defecated all over my room. I could tell she wad sick because it was all diarrhea so I did not get onto her, just cleaned up and went back to sleep. 3 hours later I was awakened once again, I tool Dott outside and went to clean the mess. After flipping on the light it was clear that this was no normal diarrhea, it was blood. I thought maybe my eyes were playing tricks so I got down and smelled it and sure enough it was one big puddle of blood, almost no fecal matter in it. Scared to death I grabbed Dott and rushed to the vet. They did a parvo test which came back negative and suggested it may be a parasite. The vet did not seem to concerned so it calmed my nerves. He prescribed these...
Panacur 3cc once a day
Pro pectalin gel 3cc every 8 hours
Metoclopramide 10mg 4x a day
Chlorpromazine 25mg 2x a day
SMZ/TMP. 480 mg 2x a day
He also gave her a shot before we left to help w nausea so she could keep her meds down.
I waited an hour after getting home to give her her first dose. I bought canned dog food and mixed it all in. She would not touch it. So I got lunch meat and wrapped it up, she still would not touch it. I ended up having to lob the pills into her mouth and stroke her throat. I felt awful doing this. The liquids were in a syringe and easily given. I left her outside and watched out the window as she obssessedly dug a hole. Once satisfied she plopped down it. She had only ever done this once before and it was due to a pregnancy. I was scared. I gave her her second dose of meds 4 hours later and called my boyfriend to sit with her while I was at work. When I checked in he said she had burrowed under my couch and wouldn't come out. By the time I got home she was lethargic, drowsy, her pupils were huge and she occasionally misstepped as if she were drunk. I continued her medications as prescribed. At 2 am I awoke yet again to a horrible smell. If Dott was not in bed with me then she could be found under my bed and that's exactly where I found her... Dead. I am so confused about her death. People were always so amazed to hear she was 9. She was so active and had seemed so healthy. Maybe you can shed some light for me. I just hate to think that I was force feeding her these pills and they could be the cause. It all seemed to happen so fast. I miss her, I just hope I did everything I could. Thank you so much for your time.

Thank you so much for your time. I am relieved that the medication was not a culprit. She was an amazing dog. I really appreciate your website. I only wish their were more vets/people in the world like you, willing to dedicate free time to helping others. Thank you again,
Christina