A couple of things worth addressing in this post!
For actual data instead of flying blind, certain medical offices and gyms keep body composition scales on hand that split your makeup by region, spitting out a printout each time you use it.
On the flip side, yes, if activity levels stay low and exercise is minimal, there's a real chance of losing the wrong kind of weight, but if your movement stays consistent whether or not you're on the medication, it probably isn't something to lose sleep over, though nothing here is absolute since every body and activity level differs.
35 lbs is genuinely a big deal, congratulations! Hope you keep pushing forward if that's still the goal!