ILL street dog?

Thers a nine month old female street dog . I gave her 1/2 of 12 mg ivermectine orally,then i sent her to an animal shelter ,they gave her an ivermectine shot. I got her released after 10 days as she didnt seem too happy wid so many dogs. i never met the vet and the istants released the dog saying her course was complete. But i descovered her body was covered with mites.After coming back she has been v low in energy ,always lying down.her heat had also started . Then i consulted private vet who said oral medication was not good enough. so i got her 2 more shots.but they didnt even do a proper physical examination to see why she was low n kept blaming heat and shots.so i took her back to shelter vet who examined her and gave anti allergy & anti-biotics and asked me to get her a fourth shot. should i do that? dsnt seem right. shd she get a blood test to det wats wrong? y is she so low heat started 2 weeks back n she spotted for 3 days only. wat cld b wrong.what prodedure shd vet follw?