Whats wrong with my puppy?

I found a puppy back in the early days of October (we estimate him to be over 8 weeks of age) and I have been treating him for sarcoptic mange and he has been doing well. But yesterday I noticed his back end (hips and back legs) seem rather small and he walks awkwardly and his tummy is bloated sometimes. Do you know what could be wrong with him? PLEASE note that he HAS been wormed, this was what I suspected at first and I also did research on a condition called Bloat but it doesn’t really say anything about the back end being small. I’m going to feed him less and give him time to digest his food before play but does anyone have any suggestions/ ideas for home treatment or what could be causing it?
What I meant by (he has been wormed) is that he is wormless I’ve treated him and given him is puppy worming meds already hes up-to-date. And sadly I cannot take him to the vet (you wanna pull $200 bucks out your ass for me to take him I’ll gladly take it) but my cousin is a VET and she will be checking on him I just wanted to see if anyone els has had simaller expereances.

Nobody here can see through the monitor so a diagnoses is not possible. Even if someone offers suggestions, they could be wrong and following any advice here for your dog’s problems could make things worse.The best place to get answers about your dog’s problems are from your vet.
It really sounds like the dog is in need of vet’s attention, please take him asap.