Trying to conceive at 41 years old

Jovski
I'm going 42 years old on the 3rd week of this february. Still trying to conceive. Last May 02, 2016 i got miscarriaged of my 2nd baby. So sad because until now i'm not yet pregnant. So tired of waiting & trying to conceive. My question is... Why my period always came early sometimes came late i thought i was pregnant but then is not?