Sophie,
you should see a doctor and have images done of your head and neck. What you are describing can be tmj, sorry to say, but you should be checked out. Don't be surprised if doctors can't or won't tell you it's tmj once they have checked everything out. It's an unusual medication condition that crosses the line into dentistry even though it's a joint(s).

Once you get looked at, if they can't help you, search for a tmj dentist. You probably will need a bite splint. A muscle relaxant to take at bedtime might also be a good suggestion. If the first kind you try doesn't work, try a different kind. It took me 4 tries to find one that did help - zanaflex.

Meantime, use lots of moist heat and/or ice, eat soft foods (no gum chewing), don't open mouth too far even for a yawn, watch your posture (especially at the computer and a desk - check pics at nismat.Org/ptcor/tmj/). Ibuprofen or vicoprofen tend to work better as pain meds but should be taken with food.

I hope this helps get you started to feeling better. Don't listen to anyone who suggests surgery or braces at this time. Conservative methods do work the best.

God bless...
Carol