Now I know I am on the boards too often - you're post is very similar to another member's post that is posted under the Dental Problems forum on the Health Boards. Only she is having a similar problem on the right side. So forgive me - but I copied and edited my response to her for you below since I thought it might be of some help. The only other thing I might add to the response below is that a night guard or splint may help as well.

It could be a mild form or flare up of tmj induced by a change in your bite (how your teeth meet), clenching or grinding your teeth in your sleep or even during the day (maybe due to additional stress). Since you are pg the best thing to do as a "home remedy" is to apply warm moist compresses or a heating pad to the area, especially before going to bed at night and do some gentle massages of the area to try and relax it. You could also try changing the position of your head and neck when sleeping - which I am sure by now is already causing some discomfort - but a cervical pillow may help ensure alignment of your neck and jaw when lying down and aleviate any pressure being caused by your condition and current sleeping position. If it continues or becomes worse check with your dr before taking any type of anti-inflamatory meds (which should also help) which I am sure you are aleady aware of. Hopefully it will resolve itself but if not then go see your dentist and let him examine the area. Also, sometimes the weight of carrying a baby strains the alignment of the body and puts pressure on the neck and spine which can affect the jaw as well - so this may go away after you give birth. Congrats on the baby and wishing you well.