So many things here! Painkillers can produce nightmares. My DF was reliving his wartime experiences, post-operatively. Nightmares indeed. Medication can cause these side effects, so a review with your GP or pharmacist is worthwhile.
A friend who worked with dreams told me that repeated dreams return until you have addressed the problem they feature. Your brain is trying to communicate with you but it has limited means to do it. Baby dreams are about ideas you have that you are either ignoring or not getting to grips with. Being in a car with pedals too far away to reach, or you stuck in the back seat while the car hurtles along, reflects your own drive, and feelings of life being out of your control.
Our brains spring clean while we are asleep, and when we wake up in a dreaming phase we catch it in the act. It can be a privilege to eavesdrop on what is going on inside your head. We can learn a lot, so don't be nervous, welcome the insight and work with it!