Hi
It depends on whether a vowel or consonant comes before it, look at the following: regardless if it past simple/continuous or present simple/continuous
ING = If the word ends in Y, and has a consonant before it, simply add ING.
E.g ED = study > studied, marry > married
ING = carry > carrying, reply > replying
Vowel + Y
ING = If the word ends in Y, and has a vowel before it, simply add ING.
ING = enjoy > enjoying, stray > straying
hope this helps:D