Shooting leg pain, loss of strength while standing, leg giving out while walking is more an indication of structural damage as opposed to muscle strain. Not a doctor but this is what happened when I messed up my disc.
Sneezing is only 2nd to child birth on the pain scale!!!!!
Muscle relaxants with rest, try to stay off the pain killers just fools your body into letting you move around more than you should.
Get better soon we start riding next week hopefully. Man-made but it's riding !!!!