"Oh My God!, I've seen a pill press how would I know what one is if I've never seen it?"
I hope you don't really expect an answer to that question.....
What you had was GHB, but before you do it again you need to find out what concentration it is exactly. If the person you're buying it from doesn't know, you should avoid buying drugs from him in the future at all costs. If you know the concentration you can accurately measure your dose using guidelines listed at erowid (it's right there on the front page "GHB" it says, if you can't find it you need to go back to kindergarten). Using "caps" to dose is risky, especially if you're sharing with friends who could easily have varying sensitivities to it. GHB has a steep dosage curve and causes unconsciousness quite easily. Do not under any circumstances mix with alcohol.