Hi,
I went into a Botox clinical trial. They gave me 20 injections in my face, neck, and shoulders (small and not nearly as bad as a migraine

It takes a couple weeks to work on the headaches. Well, it only worked really well for about a week for me (one headache during that week) and maybe b/c I was still excited that it may fix my life long migraines. I went from headaches 65% of my days down to 40% and the ones I got were less severe.
I didn't have severe muscle problems, but I couldn't raise my eyebrows for about a month and a half. My shoulder muscles also got tired easier (maybe you wouldn't notice, but I'm a dancer and so I did.)
The nurse said it only worked for about 10% of the people who received it and it wasn't complete in anyone.
But it may work and there is little to lose! Good luck!