Clown fish question

[hummer]

My clown (female) has been acting somewhat odd lately. Not sure if she's sick or pregnant. Her belly has become very big and yellowish on the bottom. She floats on her side at the top tank quite often. She still eats. The sand in the corner where she and her boyfriend hang out is all dug out. I don't see any increase in aggressive behavior towards other fish that swim close to them. If she is pregnant, should I throw in a piece of PVC so that maybe she'll lay her eggs on that? She has never laid eggs in the 4+ years that I've had her.
The lights are off now so I can't take any pics.

Any ideas?
Thanks.