The same happened to me when i quit smoking weed a few years ago. Its normal. Your mates wanna go somewhere they can sit and get drunk as part of a group. Not feeling alienated by someone. Do you seriously think your mates could come round act like drunken fools in your lounge and you'd be OK with it? Believe me you wouldnt be, youd spend the whole night lookin at them reminding yourself why you gave up drinking in the first place and hurrying them out the door!