Hello Organicsmuncher, Sounds like you have 2 problems here - waking to go for a pee a lot and the nightmares.
It's likely that the stress you're under is causing your nightmares, so addressing that will help. You could also write down what's happening in your nightmares but don't worry if it doesn't make sense to you. Try keeping a journal of what's going on and how you're dealing with it. Talk to a counselor or trusted friend or try meditation or yoga to bring your stress levels down.
For the getting-up-to-pee problem, this will disturb your sleep and probably means that you're not getting the right balance of the right phases of sleep. This can add to your stress levels because proper sleep means you can deal with stressors better.
Keep an eye on the amount you're drinking in the day (if you drink a lot you'll pee a lot) and if possible avoid alcohol after 6pm and try not to drink anything after 7pm (assuming bedtime is after 10pm). That may help.
If it doesn't then see your doctor as you may be making too little of a hormone that regulates how much we pee.