Is it possible for the diamox to stop working even though it has been working in the past? 

In the past week I have been sleeping a lot more hours every night, where as before I couldn't sleep anymore than 6 hours a night.

I have started to get pulsating tinnitus again, which I haven't had for quite a while. 

I have also started to feel hungry again, instead of having nausea or no appetite. This one actually started a few weeks ago.

I still however get tingling in the feet, mostly at night when I'm trying to sleep. Also wondering if weight loss can affect it as well, as I have lost 25kg (53lbs) in the last 6 months. 

Thank you in advance for your help!

well your sleep apnea is probably better which is probably why you are sleeping better.
what makes you think the Diamox stopped working?  if you have lost weight, you are on a higher effective dose of Diamox, more milligrams per kilo of body weight.

I have heard some members get used to it and have to increase the dose, but I would have thought that you'd need to decrease due to weight loss if anything. Definitely would contact the prescribing physician to discuss the return of your symptoms, and make sure they're aware of your weight loss. Good job, btw.