Luna broke her left hind on July 1st and after determining it was osteosarcoma we had the leg amputated on the 3rd. She underwent a full course of chemo (6 treatments). Near the end of chemo she started to yelp at random times (in the middle of the night, when she was walking, sometimes when sitting and people were petting her). At first we had no idea why. We took her to the vet and to her physical therapist, but she is a nervous and reactive dog (screams and throws herself around) so they have a hard time evaluating her and don’t know what is going on. We started limiting her walks. And then she started deciding she did not want to get up in the morning and did not want to go anywhere when we wanted to. She would still get up to go potty, drink, wander around, come to cuddle. 
This corresponded to the weather getting colder. She started looking at her remaining hind leg and butt after yelping, and now 6 weeks after her last chemo appointment she is no longer getting up to relieve herself or get water. She still gets up to change beds occasionally. She is 90 pounds and is on 75 mg of Carprofen 2x a day and 300 mg of gabapentin 2x a day but we just moved her up to 3x today. She has also only been on the gabapentin for 1.5 weeks. Is there anything else we can do. Until yesterday she still seemed happy, but now she is acting depressed. If this is her end I don’t want to put her through more pain, but I also don’t want to give up to soon if it’s just a sore muscle etc. we are having a hard time getting her to the vets office now as she doesn’t want to move and she over reacts when we try to get her to do something and ends up crying and hurting herself worse by flipping out. I am just not sure what else to do.