Yes, that does sound like pregnant animal behavior. I might get a breeding trap or such to put the fish in for a bit to see if that's what's wrong.
If it's always been acting this way - and it's not pregnant, then it might be experiencing stress and some illness - keep an eye on it, monitor the conditions carefully - and consult your local fish store (not a pet superstore, but an actual aquarium shop - pet superstores don't train their people enough) If you make any change to the conditions of the tank - then make them GRADUALLY - otherwise, you will have a lot of dead fish.
If it's always been acting this way - and it's not pregnant, then it might be experiencing stress and some illness - keep an eye on it, monitor the conditions carefully - and consult your local fish store (not a pet superstore, but an actual aquarium shop - pet superstores don't train their people enough) If you make any change to the conditions of the tank - then make them GRADUALLY - otherwise, you will have a lot of dead fish.