well from the point of a guy, i would say you should tell him because.
1. You owe it to him to tell him and let him decide what ever he will do.. you were drunk, and his so called friends took advantage of you.
2. You did not do too well to go to a private party, be it with his friends or who so ever. and you should not have been so callous to have gotten drunk to a state where you do not have control over your senses..
so my dear its better you hurt him by telling him the truth, cos at this point you have the advantage of sugar coating the whole whole story, that you were drugged and abused...
but if you let the tape get to him first, i am sorry it will be near impossible to salvage your relationship at that point.
so my advice is that you tell him..
#BlazaeR