My Pomeranian has bad intestinal issues, vets on here please help?

I got my female pom at 10'weeks old, the day I got her she was having bad diarrhea. The vet figured she has a sensitive stomach because when they did a fecal test nothing showed, so she has been on a high fiber low residue dog food. It's helped but not completely. Two weeks ago she was having blood in her poo, so I took her to the emergency vet. They found out she had giardia. She's been treated, and she finished the meds for giardia last week and the second medication yesterday. Now she has bad diarrhea again, to the point where everywhere she sat in my living room had a poop stain. I've noticed she is dragging her butt across the grass when she goes as well. Do I need to get her retested for giardia? What other explanation can there be?