Have you taken your measurements yet? I didn't until I was about a stone into the journey and I wish I had earlier because I still have issues noticing the difference even now (and I'm nearly 4 1/2 stone gone. There is a HUGE difference in me - I'm 5 sizes smaller) because I'm still fat and I see me every day. If you haven't done it yet, go and do it now - arms, chest, above your waist, waist, hips and thighs.
Realistically I didn't have my first clothing size drop for about 2st - mostly I think because I'd been stuffing myself into clothes that were a wee bit too small (and were stretchy) for such a long time that I was probably a size bigger than I was wearing to begin with. I have noticed the sizes dropping faster since the first one though, which is lovely.
One and a half stone is BRILLIANT - and will have come off of all sorts of places, your back, fingers and toes, arms, chin, jaw - and even if you're not visibly noticing yet, your heart will definitely be noticing the reduction in the work it has to do just to keep you alive.