Cat pees when you pick her up

We have a female cat, just over 1 year old, that we adopted about 4
months ago. A few weeks after we adopted her we discovered blood in her
urine and took her ot the vet. She was prescribed antibiotix, which
seemed to help for a while. A month or so after we finished the
antibiotics she started showing symptoms again, so we had a culture and
sensitivity test done on her urine and discovered there is no bacteria.
She was put on Amitriptyline gel and we have been giving her this for 2
weeks now. She seems better in most ways (has stopped peeing over the
edge of the little box, no blood in urine, almost 100% back to her
playful, affectionate self) except for 1 problem. Three times now in
the last 5 days she has pee'ed when we pick her up. I'm not talking a
dribble either - it's a good stream! The vet had never heard of this
happening. I was wondering if anyone out there had experienced anything
like this.

She does have other odd symptoms that may/may not be associated with
her bladder problems: she grooms herself a lot, also scratches a lot
(she does not have fleas - we've had her checked). Also, she has had
runny stools ever since she went off of the first round of antibitoics
(we have given her acidophilous and pro-biotics, but this has not
cleared up).

Any ideas/suggestions would be greatly appreciated.

Thanks,

Jacqueline