Harder to conceive on third child?

Jade

I am currently 10 dpo, 3 days from expected period and my husband and tried to conceive this month right on my ovulation day and the days prior. With my first two children we conceived on first try and were very fortunate. However, I have had negative pregnancy tests, and PMS symptoms so I am assuming this month did not work. Though I know it’s normal to not conceive on first try I can’t help but feel like something is wrong as our first two tries we got pregnant right away. Thoughts anyone else experience this?