Of course it is important to rule out other conditions or problems that can be causing this. For myself though I have RSD and PN I have severe edema in my feet. Especially in humidity I go up 2 shoe sizes. I also notice that it feels like have lack of circulation in mylower limbs. Other then humidity I don't notice a connection though sometimes being on them too much causes this as well. Overall I try to watch my salt intake. I do try to keep moving so I wonder are you able to do some activity or even go into the pool? If you keep your feet up does it help? Since your doc thought it may be from the meds did he feel you should switch meds or wait?
I hope you get some answers and of course relief.