I definitely think you need to check with the doctors again soon about rechecking your levels of medications. I'm not sure when you last had them readjusted, but even losing a little weight can change how much is needed or how often.
I can only say that for me... regular exercise and losing weight makes my monthly woman schedule more on time. I am on birth control, but even so it wasn't always that regular. Since even losing a little bit of weight and being regularly more active my cycle is starting to become more normalized.
Also, about the last 10 pounds being harder... it can definitely be MORE than the last 10 pounds. People tend to say "The last 10 pounds is harder to lose" as more of a generalized statement, just to say that the last bit of weight sometimes comes off slower. Not that it's always 10 pounds that's harder. You've already lost an absolutely amazing amount of weight, so your "last bit" could be 25 pounds instead of 10 pounds. Don't be too discouraged!
You've done fantastically. The weight is still coming off, even if it's a little slower. You WILL get there.