If you have a female guppy, chances are it is pregnant. Very hard to find one that isn't :lol:
They can drop fry every 4 - 6 weeks and can carry sperm for several months so don't need a male very often (lucky girls)
When about to drop the body will be very fat and you can often see the black dots of fry eyes through the belly of the fish. The gravid spot (where they come out) gets bigger and darker at this time (I imagine the fishy midwife saying "You are .5mm dilated dear, not long to go before you have to push!")