If you have to come on here and ask how much to take, I definitely wouldn't take any more than the 3mg you already took, which is a lot for someone new to benzos, particularly if you don't have much of a tolerance to the 8mg of bupe you shot earlier...It's not very recreational as far as benzos go, but it will greatly increase the effects of opioids and the combo you did could in fact, be really dangerous and cause you to blackout and possibly even OD...
The only thing that can make bupe dangerous is mixing it with benzos, particularly if you're naïve to each...which you seem to be, no offense. You're probably starting to feel very floaty and tired as I type this, possibly catching deep nods and have a strong desire to just drift off to sleep. I'd actually be very careful and at least tell someone what you took....You could suffer respiratory depression and stop breathing if you fall asleep. The potentiation between those too drugs may be a lot more than you bargained for.