Icing your neck may help, and might also reduce the headaches if they are exacerbated by the whiplash.
I had memory problems too, if this doesn't improve with rest, consider asking your doctor for a referral to a speech pathologist that is familiar with mTBI. Speech pathologists can work with all kinds of cognitive deficits, not just speech problems. Speech therapy helped a lot in my memory recovery.
Make sure you are well rested first.
Did I mention rest is important?