I took my 5 year-old, rescued ball python to the vet last Monday for a check up and a fecal float. It was determined that he had two kinds of parasites - pinworms and and something with a T... Prior to this visit he had eaten at least 6 consecutive meals and not had a single bowel movement. (This was the cause of the vet visit.)

She gave him a small syringe of medication and told me to come back in a week for the second de-worming. She also forced him to poop by squeezing on his abdomen; healthy poop was excreted.

Within a few days, he then pooped on his own. The poop was pretty solid and seemed to be healthy; I was pleased. Now, however, I am worried. He has pooped three times since that vet visit, and two of those poops are VERY runny and gross. He is visibly thinner, and is getting loose skin all over his body. He is losing weight in what seems like a small period of time. I am wondering if he is having a weird reaction to the medicine? Or if maybe he is just flushing out parasites. I have no idea how this medication is supposed to work, and I can't call the vet until tomorrow since today is Sunday.

Does anyone else think this is something I should be concerned about? I tried to feed him last night and he was very reluctant to take it. He didn't bother to come out of his hide, and when I moved the mouse towards him, he recoiled in fear. This is a snake that isn't even head shy, and has NEVER refused a meal. He finally did take it, with much poking and prodding. No regurge so far...

I want to take him to a different vet, but I feel like I need to finish his deworming first. If I refuse to go back to his old vet before the three-stage medication is completed, will there be ill effects for the snake? Unfortunately, I don't know what brand of medication is being used. This vet didn't tell me ANYTHING. I have no idea what went on while I was there; she didn't include me in anything.

Please guys, tell me I shouldn't worry...
(And before anyone asks, bad husbandry is not an issue. Everything is spot-on.)