Bladder Problems?

My cat has been acting funny the last few months. She meows quite often
for no reason- usually when she comes into a room. 2 months ago she
started to urinate on the floors or on piles of clothes/towels on the
floor. I've noticed that many times, whether she's outside or inside,
she squats to urinate, but nothing comes out. She doesn't act funny, or
in pain or anything otherwise. We have the clumping litter, and I know
she IS urinating based off the clumps in the litter box. Is there a
reason to be concerned, or, is she just being a funny old cat? She was
a stray, so I believe she's about 7 years old now. Any help is
appreciated...