Advice wanted please.

Sounds like he wants to sleep around and most probably has certain people in mind already, or has gotten cold feet over something maybe you guys got too comfortable and he wants excitement and to have sex with lot's of people before a serious long term relationship. This is obviously not to do with you, and unfortunately I think he's ruined what you had. Don't let him sleep with other people and come back to you, I know it's going to be hard as hell but make him either beg to be back with you or move on. He told you it's over on tuesday morning out of the blue which must have been horrible for you, and by the looks of it (as a lot of people in your position would) you're gunna try and make it work which I very much do suggest, but be very blunt for him and ask him where he see's your relationship with each other going, I'm not sure staying friends right now would work as you could get stuck in a limbo state where you're still really attached to him but aren't with him, if it isn't on the cards get closure and get rid - he's done it for such a silly reason and I feel you are vulnerable due to you being best friends with him as well, I feel for you ! This may sound somewhat cold but I want you to take off the rose tinted glasses and consider that while you I'm sure can still picture your amazing future together with him, he's thinking of ****ing other girls. Best of luck, I hope it either works itself out or you can deal with it