When will I get to sleep again?

At about two months of age, Emilia started to sleep about 5-7 hours a night.  I was elated.  This was heaven to me, so I had no complaints.  Unfortunately, this 5-7 hours a night was happening in her swing.  No, the swing wasn't swinging her to sleep.  She just really liked the cozy cradle-like swing.  At her two months doctor appointment her pediatrician tells me that I really need to get her sleeping in the crib before 4 months, because it will be more difficult after that point.  Well, I waited until 3 months to start her sleeping in her crib, and it's been a battle ever since.  She has had a few nights in the last three weeks of 5 hours and one night that she actually slept 7 hours. Of course the one night she sleeps 7 hours straight is when my husband was taking care of her!  The rest of the nights she is waking up every 3 hours.  It's like she is a newborn again!  It's painful for me.  I want to throw myself out the window sometimes, because I'm so frustrated that she keeps waking up.  And yeah, sometimes I want to shake her with frustration, but I don't.  Every time I would see an ad or hear someone say "never shake a baby" I thought to myself...Who would shake a baby?!   Well, now I know how close parents can get to this point without even realizing it.  And after talking to other mothers, I'm not alone.  This week has been especially bad, because I think she is starting the teething process.  I didn't know it would happen this early, but I see some signs: drooling, slight fever, pooping a lot and fussiness. How long does this teething process last?  I'm not seeing any teeth emerge.  I'm tired, exhausted, and worn down.  I'm just a better mom when I've had sleep.  I really shouldn't complain, because I don't have a baby with colic. I hear that can be rough.  She is happy most of the time and for that I am thankful, but please let me sleep more than 3 hours in a row very soon.  I'll even take 4 hours! What is really sad is that even if she does sleep more than 3 hours, I will wake up during her normal wake time and will not be able to go back to sleep.  I start waiting and expecting her to wake up soon and sometimes this can last an hour of two.  That is one hour too many of wasted sleep time for this tired mom.  Tonight, I will again be hopeful that tonight is the night that she and I will both sleep through the night.  Wish me luck!