Why did your therapist recommend you massage your jaw from the inside? I'm curious because I do this and have never heard of anyone else doing it!
I have a recurring knot in the masseter muscle on the left side. It gave me such bad headaches (and eye aches and ear aches), a neurologist diagnosed me with Trigemenial Neuralgia and prescribed me some heavy duty anti-epilepsy (or was it anti-seizure?) drugs.
I felt something was off with the diagnosis, and continued my own research. Well, I'll be damned, self-massage has cured all of my problems. No pain in my head, eye, or ear since July/August.
I also massage my temporalis and sternocleidomastoid daily. I use a tennis ball to self-massage my upper back. I have poor posture and all the muscles are interconnected and affect each other.
You can do it. When you see how much better you feel (and really, how simple it is!), you'll get over the ickiness fast!