Holding tail to the side?

Hi all, hope maybe you can help me with something....

so yesterday Dotty started carrying her tail to the side. Mostly to the right but sometimes to the left. You notice it when her tail is either level or down. 
She doesn't seem to have any pain or be in discomfort, I have handled her tail, rear end etc and she is not pulling away. She is as happy and bouncy as always. Yesterday she was scooting a little and sitting down sharply and looking at her bum. Made me think of worms though her wormer is up to date. Have not seen her scooting today at all and only sat down a couple of times. 
I wondered maybe if it might be her anal glands? Supposedly it can feel quite uncomfortable if they get full. Her stools are always firm and have been of late also. 
Only other thing I thought of was she had a good hard run at beach yesterday, maybe she has jarred or bruised it? 

Anyway she is going to vets tomorrow for a health check, just happens to be good timing as part of her health plan anyway. 

I just wondered what other peeps thoughts are and if anyone has come across this before? What was the outcome?

Thanks in advance