When our Yorkie was a year old, she had surgery to remove her anal glands. Over the course of that year she went from needing the vet to express the glands every 6-8 weeks to needing it done 2-3 times per week! After the surgery the vet said that it was a problem that never would have resolved on its own.
Our only issue now is that she's afraid when she has a BM. She starts on her potty pad but then acts like she's scared and starts running while going, often leaving a trail of poo from the pad.
Last week my Cavalier decided he'd rather not go outside to potty so he went poo on the downstairs potty pad. Puff, the Yorkie, saw me praising Luke for going on the pad (and not in the floor which he does occasionally). For some reason she never has a BM downstairs, she always uses the pad upstairs. A few minutes after I took care of Luke's poo she came and got me, and sure enough she had had a BM on her pad downstairs. She was prancing around like she was a little princess so proud of herself! She is the funniest little thing--she keeps me laughing all day!
Good luck with the anal gland issue. I was very disappointed at the lack of good info available on anal gland problems. If I can be of any help please PM me.