First off aces just chill. Telling them apart is easier than you think. I'm coming up to 4 weeks flower now on my first grow and just like you I was shitting myself that it was going to be a nightmare telling them apart. I envisioned my entire crop turning to seed like all the horror stories you have probably heard.
I won't bore you by telling you what to look for as I know you've probably looked at several different pictures. All I will say is that 2 weeks into flowering every single male was removed from my garden. The trick is not to wait too long. I was pulling males within the first week, I didn't wait for the bunches to form. Just one ball could do it for me. The best thing to do is wait until a female starts to show, you don't need the pistils to be coming out, you should be able to tell from the very shape. There is a marked difference between the two.
The clone king was supposed to come and show us the males but we'd done it all by the time he visited, he was well impressed. With what, I don't know because telling them apart is a piece of piss.
Oh yeah, how many plants you got? You've gotta watch out for hermies too.