Hello ma'am and welcome.
Firstly, I think your doctor needs to concentrate on regularizing your menstrual cycle before giving you to go ahead to try to conceive, as this is primary.
The second thing, adequate hydration advised now is not just to avoid dehydration
byt possibly to prevent the formation of stones in the renal tract or to help with their expulsion. Please continue to drink plenty of water and speak to your doctor about correction of your irregular menstrual cycle.
Hope this helps.