False negatives!?

Hi all, this is my first post here, and only recently ttc so this is all pretty new to me.  My cycles are a little irregular, usually no longer than 26 days. I had sex at my peak fertile time on 29th July, and got a negative pregnancy test result yesterday :( is there a chance I tested too early and it could be positive?? I am on day 26 of my cycle now. Thanks in advance!