Trying and yet still trying

Tracie • Married,and had our son 11-22-14 and our daughter 8-5-16
My hubby and I are still trying.. We been married since sept! And been trying since August... Still nothing.. We are 27 and 30 in age.. But since I am a twin I am wondering if there is anything to do with that.. My twin sister already has two kids and she never had to track anything.. They were just "accidents".. I wish I was that lucky! 
​Is there any others twins out there experiencing the same thing that I am going through? 
​I hope to have a positive HPT this month and can test Christmas morning.. AF is due on the 21st... 
I am getting more and more fusterated each and every month when AF shows up! 
​Hope everyone has a wonderful babyful positive HPT Christmas mornings!! Sprinkling babydust***