When is the earliest that I can test?

I get really emotional when I see all these positive pregnancy tests, pictures, and announcements. I am SO happy, I mean truly happy for those people because I know how frustrating it can be. I wanted to say Congratulations to all of you. ❤ I'm really hoping that I am next with a BFP. (I hope it's this month!!) I'm on CD27 and I'm trying to be hopeful and patient... My periods are irregular so I really need all the prayers and baby dust in the world.. When is the earliest you think that you can test and possibly get a BFP??