Hi Everyone i Have a Question and need advice

I have a appointment with my doctor next week but my question is my period is regular it last about 5/6 days but my fertile window starts the day after my period ends and my LP is about 18 days could this cause TTC problems me and my fiance have been trying for about 2 years now i was cleared from my obgyn and his test came back good but havent been to a fertility clinic yet but in the mean time i wanted advice from you ladies Thanks so much