Trying to conceive

Hi my name is sheila im 29 years old hapilly married 7years ago my son of 3 months old passed away he was born early 6months 5weeks born 2lbs 2oz 4-10-08 passed 6-16-08 he was my first after that i have not been able to get pregnant my periods are irregular  but know my doctor put me on meteformin to regulate my periods because she says i have PCOS and know its been 3 periods in a row since dec im so happy i tried conceiving this month but just took a test and it was negative im feeling so down i dont know what to do.
Its been so hard ..