there's truly no "normal" or certain length of time it could last.. some never experience it, some have it during their entire pregnancy, etc.
with my first son I only suffered from week 6-10, now with my second son I suffered from week 6-16 or so.. and that was rough was a baby on my hip lol my 1st is 14 months, and I'm 28w1d at midnight. every pregnancy, baby, woman, etc. is totally different! just make sure you're staying hydrated & such.. and speak with your doctor about getting some relief!
good luck, hopefully it'll pass for you soon!
*with* a baby on my hip. (sorry, preggo brain/typos)! ((:
It is normal pregnancy differs for each woman. My morning sickness just subsided abt three weeks ago but it comes and goes still. I'm 24 weeks