12 months 😞 feeling sad

Been trying for 12 months now. Period came today 😞 so hard to stay positive!
Wish it was as easy as pushing a button. 
How do you stay positive. Brother and his partner are expecting in March. They weren't trying and even had the coil in at the time they found out. Sister managed to be pregnant twice in about 15months. I have two lovely nephews and a niece about to appear. Happy for them of course but is it ever going to be my turn. 😞 x Anyone have an advice or tips that would be great? X