Probing is not the only way to sex a bearded dragon (and not recommended as it can hurt the dragon), they are actually quite easy to sex, but I would wait till they are atleast 6 months old. The following link
http://www.dachiu.com/sexing.html from dachiu has pics to help you sex your dragon. A male dragon will have two bulges at the base of the tail with a valley inbetween them, and a female will have one bulge in the middle at the base of the tail or nothing at all. I hope this helps, and if you are still having problems sexing your dragon try posting a pic of the area I described and me or someone else on here should be able to help you figure out what sex you have.