Hey
I've had altitude sickness before whilst on diamox as well,
It was a couple of years ago for just over a week and there was quite a few side effects which weren't particularly harmful
The Diamox does give you a really weird tingly feeling in your fingers and toes and sometimes around your face, its not unpleasant or anything just a really strange sensation,
and it does make you need to pee A LOT but these were the only side effects that anybody in our group experienced
Diamox doesn't prevent AMS it just reduces the risk of getting the serious symptoms
Even though i was taking diamox i still got atitude sickness and i have low blood pressure too like you said although i've got no idea how much this contributed to it
The only way i can describe it is like having bad flu and just feeling really really weak, i had a couple of panic attacks while we were at the highest camp which had never happened to me before or happened since then.
Coming down out of the altitude makes such a big difference, you can feel energy coming back into you
If you've got any questions pm me, although i don't know much more about it all, you should probably talk to someone experienced like the others said
Hope that you have a great trip