if you haven't moved it out of the pot it came in and you've had it for more than a month, it's probably root bound.
you can tell for sure if you see roots growing
out of the bottom drain holes. if the pot doens't have drain holes, turn it on it's side over a piece of newspaper and gently put a knife into the side of the pot just at the edge where the soil meets the pot - move the knife all the way around the edge of the pot to loosen the soil away and then gently tap the bottom of the pot so that the plant
/soil come out. you can give a gentle tug on the base of the plant
(where it comes out of the soil) to help it move out of the pot. if you see a ton of roots all around the outer areas of the soil, then it's root-bound and a bigger pot is in order.
gently break apart the bound roots, get some good soil and a larger pot and move it into the new digs.
it should bounce back just fine!