Yes, you may need some denture adhesive cream initially as the area is healing. What happens is that when a tooth is removed, the bone will resorb (jaw bone that is) and change shape. Since the denture relies on the jaw bone for support, that will tend to loosen a bit over time. You should return to your dentist every now and then for an adjustment to tighten them up. It takes a few months for the bone to stabilize at which time, you will notice you'll need less and less adjustments and they tend to stay tighter longer.
As for your denture, I would recommend taking them out at night and brushing them with water. You should also place the denture in water anytime its not in your mouth.
I've just been at my dentist as I was alos due a check up anway. The discomfort is easing quite a bit but during my check up my dentist noticed some puss oozing from the sockets of the top two. She was saying this could well have been the cause of the discomfort.
The denture fits great especially if I use some denture fixing cream. It stops me from playing about with them as well! The more I wearthem the more I'll get used to them, but finding the denture fixing cream works a treat I'll continue with that. As I shower daily I'll let my dentures soak while I shower and then clean the teeth I have in my mouth!
I'm not sure why you would faint/have shock after an extraction. That is a bit unusual.
As for the source of pain, its possible that there may be a small piece of the tooth remaining in the area that could be causing the problem. Also, the fit of the denture may result in some trauma in the area which may take a few more days to resolve. For the meantime, monitor the pain and inform your dentist is the pain increases more than it already has. You may want to discontinue use of your denture and maintain as good oral hygiene as you can in the area.