I use both a high CBD oil for pain and a regular THC oil at night to help with sleep. There are two consequences to these. First, I have difficulty peeing even with a full bladder. This isn't terrible, but it can be annoying (note: some people are affected this way and others seem to be okay). Second, while both cause dehydration, for me the THC oil results in pretty intense dehydration. It's profound enough that it has impacted my bowel movements (I take Lax-a-Day to counteract this.

Your dehydration is from the cannabis. Try and drink more after you use, but in my experience this doesn't make a huge difference. If you want to test it, lay off the weed for a bit and see.