I'm so sorry to read about your problem ali-in-pain. It sounds like your disc is trapped in the closed position. I'm not a doctor or anything the like; just a long-time tmj sufferer, so my thoughts and recommendations only come from my experiences. My tmj is currently under control. So, on to my recommendations - use lots of moist heat directly on the jaw and neck muscles. If you notice any extra swelling, though, stop the moist heat and use ice for 15 minutes at a time. Ask your doctor for a prescription of valium or zanax to take at night when you go to bed. You might want to consider a muscle relaxant also for a few weeks (zanaflex works the best for me).
And since you have an upcoming trip, I recommend that you go to a physical therapist or massage therapist who is educated in tmj. If you go to pt, ultrasound is great and then massage (i don't recommend any type of exercises at this time, your muscles need to relax). Your doctor will have to give you a referral to a pt but not for an mt.
I usually don't recommend a narcotic pain medication since our bodies are so different and we react differently, but we have to get you well for your trip. I highly recommend vicoprofen (not vicodin). I have found it to be a god-send when my tmj flares up. It reduces swelling with the ibuprofen and the hydrocodone relaxes my body like nothing else allowing my jaw to relax. I have actually felt the jaw(s) go back into proper position about an hour after taking it. It is an additive medication so it must be carefully monitored.
Try and keep your body relaxed and free from all stress, and watch how you hold your neck and head (sit straight & tall with the chin kept down.) watch that your shoulders do not ride up and the face (head) should not be extended out towards a computer. Keep back and down. And even more important is your mouth - keep the teeth apart, relaxed, with the lips together (or slightly apart) and the tongue resting on the roof of your mouth.
I hope and pray that something helps you get that mouth open. Once you do get it open, be extra gentle with your jaw by eating softer foods. N.O gum or ice chewing or anything hard or chewy (no steak for a while).

have a safe trip.
God bless...
Carol