“I have not woken up with so little back pain in a long time.”
I heard this in a mattress commercial, and it sounds wrong to me. What would be a better way to phrase this sentence?
CESS!!
Youre back!
Whats bene going on?
When did you have the baby?
Missed you!
Its been a long time since I’ve woken up without back pain.
or, “It’s been a long time since I have awkened without back pain.”
or, “awakened”
my back hurts right now.
It’s been a long time since I have had so little back pain after waking up.
The meaning of that is the exact opposite of the OP.
But the grammar is correct.
The grammar is fine in the OP. What is wrong with it?
MacGuffin, your “It’s been a long time since I have had so little back pain after waking up” is correct but very cumbersome. Stick with the original.
I think the original is correct, but try:
“It’s been a long time since I’ve woken up with so little back pain”
“My back normally hurts more than this when I wake up.”
“Woken up” just sounds wrong to me, but if it’s ok, then ok!
Vanilla, I’m here now and then. I had the baby on September 22, at 12:50 am. He missed my wedding anniversary by 50 minutes (thank God!)
You are always welcome to IM or email me, and of course, read / comment on my website. 
OMG, worlds collide. Came across your website from another one I regularly read.
Congrats on the baby.
The grammar’s correct but it’s a tad clunky to my ear.
Congrats!
I dont have your e mail anymore. i think I still have your home address.
4 kids!
Yow!
Still have your figure?
Oh, yeah, Primaflora? Which one?
Figure? I don’t think I had one of those to begin with.
As far as I can parse it, “I” is the subject, “have not woken up” is an intransitive phrasal verb, and “with so little back pain” and “in a long time” are both adverbial phrases. Looks fine to me. “woken” is a legitimate past participle of “wake” (cite: Word Reference).
This page includes a usage note from the American Heritage Dictionary about the usage of woke/waken/awake/awaken which tries to draw out some differences. It suggests “she woke up” is entirely proper usage so it would seem likely that “i have not woken up” is equally correct…
How about:
I woke up without back pain for the first time in years!