Congratulations erbear!
Whitening toothpastes do not whiten teeth. The best they can do is remove very recent staining. Patients who eat and drink staining foods, are often recommended to use whitening toothpastes during their time wearing braces, so the exposed area of tooth will have recent staining removed, and be the same colour as the clean tooth covered by the bracket. Of course this is only done if the patient has followed the instructions and had a cleaning in the few days prior to getting braces.
To whiten teeth, you have to use products that contain bleach and are in contact with the teeth for quite some time ... unlike toothpaste. Also you'd know it was a whitening product, as you'd have to fashion a mouth guard, or something similar to keep the product in.
If you have 'white' marks on your teeth, this is usually a sign of poor oral hygiene. Usually caused by sugar staying in contact with the enamel for long periods of time. Hopefully if this has happened, your ortho would have said something to you when it was first seen, so you could improve your oral hygiene.
Hopefully it's just your eyes playing tricks on you, and your teeth will look amazing when your braces come off.

Good luck!