This is precisely why I never weigh. It messes with your head!
When I realised my state of the art digital scales gave a totally different reading - 5lb apart - depending which floorboards it was on over the space of a square metre or so of my bedroom floor - I realised enough was enough!
Measuring is thought to be a more accurate way of measuring success anyway as the scales are measuring not just you but that particular day's food, salt intake, water retention - vary from one time of day to the next etc. I realised if I listened to the scales I was in danger of panicking and giving up - being back where I started. They're true diet killers!
Measurements are giving you good feedback. They're what I'd stick with. After all, at the end of all this - what matters to you? Losing inches (going down dress sizes) or what a number says on a dial?
I've been back on track just 4 weeks and wish my inch lost was as spectacular as your's! I've lost the odd inch here, and there. Your achievement is great!