TTC baby no. 1 HELP!!

Im almost 19 and my fiancé is 30. We are both in good health (as far as we know) and have been TTC for going on 6 months now. It's hard to track ovulation because my periods are a little irregular (a few days early or late- up to a week late sometimes). Has it been difficult for anyone else the first time?? I'm starting to get really discouraged that something may be wrong with one of us to prevent us from having childer. Trying not to see a doctor before December.