My initial guess is an exostosis based upon your question. What may be happening is that you are clenching frequently, putting alot of pressure on the teeth. The body naturally reacts by trying to support the pressure by placing new bone. If you can fix the clenching, the exostosis should resorb. If it doesn't, its not necessarily a problem since its just bone.
Can't tell. Looks somewhat red though. You might have gingivitis. When was your last checkup and cleaning? I would recommend that if its been awhile.
Thanks for the answer! Judging from the picture, does it look like any bone loss under the teeth?