Is my weight loss normal?

So i joined Weight watchers literally 3 weeks ago. I've been sticking to my allowence but i've kinda spoilt myself this week. It was my bfs 21st on Thursday so i allowed myself cake and such and i havent been exercising as much as i'd like to. So in the first week, i lost half a stone which i thought was pretty awesome, but im aware you lose the most weight in the first couple of weeks so i wasnt expecting to keep it up. anyways, by week 2, i'd lost a total of 1 stone and 1lb. So i weighed myself last night and according to my scales, ive lost a stone and a half in 1 week, ive literally lost 2 and a half stone in 3 weeks? I weighed myself multiple times since, and ive even used different scales incase mine were lying, and they all say a similar reading. I dont see a difference in my body weight and my clothes dont seem to be getting much baggier, but other people say they can tell.. so am i going to gain a lot of weight in the next few weeks or is this normal?