Twitching & Sensitive Skin

Hi - I'm having a problem with my 8 year old indoor only cat.

When I pet her on the lower half of her back and base of her tail, her head twitches and she has very sensitive skin. She won't even let me brush her. She does not have fleas and I'm not seeing any white dandruff like stuff on her. Any ideas?

Please see a vet for a workup.. It may just be a few crazy nerves due to getting older but it could be more serious.... NOT to scare you but similiar happened to my Gigi ( yorkie) and it turned out to be a massive tumor growing