We started young also we were 23 when we started ttc. We assumed it would be immediate success as both sides of our family are full of whoopsie babies. We were the first in 3 generations to be married before kids!!
I went to GP after just 6 months and told her it had been over 12 months. I didn't feel guilty; I knew something was wrong and I was right. If we had waited longer we would maybe still be waiting!!