I tried botox 3 times before it actually worked. Each time, the doctor upped the dosage. It wasn't until he gave me 100 units of botox (which is a lot) in my left (problem) masseter that I felt relief.
My symptoms started with what I thought was a toothache. The back 4 teeth of my lower left side were throbbing and I thought it was due to an abscessed tooth or something. In the beginning, my bite was just fine.
I had an unnecessary root canal done which only made the problem worse. After the root canal, the pain began switching sides of my mouth and more symptoms popped up (ear pain, headaches and noticeable jaw muscle pain).
About 2 weeks later, I noticed that my bite was slightly off. That's when I went to all the orthos and doctors who said that the problem wasn't my bite.
Today, I have a significant open bite. Only 4 of my teeth touch when I clench them, and now, I have to get it corrected with an orthotic splint, then braces.
I don't wear an appliance now (because they weren't helping -a bite guard will protect your teeth, but won't prevent clenching), but I do take medication before bed and during the day. I take 50mg of Nortriptyline and 1 mg of Clonazepam before bed each night, and it definitely helps.
I also take .5 mg of Clonazepam in the morning because like you, my pain progressively gets worse throughout the day. I usually feel fine in the morning, but around 5:00pm, the pain is much worse. Don't automatically assume that if you feel better in the morining, you aren't clenching, because I thought the same thing, but, after nearly cracking through my hard acrylic splint, I realized that I was in fact grinding/clenching.
Acupuncture didn't help me at all. I went to 10 sessions, and experienced no real pain relief. Myofacial release will help with the pain, but it won't solve the problem. You have to find the root of the problem and correct it.
Hope this helps