Dogs cries when having defecating bulky stools

hi. My little dog has been having problems lately(She 5 1/2 years old and 11 lbs. Last year she was crying everytime she had a bowel movement. Went to the vet and she told me that she had infection (it was all red and I had to use Panalog cream) and she also had her anal gland expressed. She was fine all summer since I walk her a lot at that time. Lately she started having the same problem again. I`ve changed her diet to high fiber diet. And started walking her even though it`s winter so to get things moving in there. She defecates a lot more since she`s been on this high fibre diet. She`s fine when it`s only small stools but as soon as they are a bit bulkier she cries. She had her anal glands expressed last december again. Her anal glands was a little red since she was licking herself a lot there. I`ve used the Panalog cream again and give her warm compresses. Another thing is that she licks herself a lot (her paws) and she makes hairballs as well. She also takes hairball remedy. But she had that problem even before she start having these difficult bowel movement. Could it be something else or could it be internal infection that she has and she needs antibiotic. She was also checked to see if there was any tumor and there was nothing.

Can you help me here.

Thanks

Cécile