J.F.
Hang in there, mama!!! Babies are HARD. Not two of them are the same. :) What I found out about my babies is that just when I thought I had it figured out (their natural schedule, what to expect, etc.) it would change. :) That makes it super hard.
Things that jumped out at me....
Babies go through growth spurts on the 3's. 3 week, 6 weeks, 9 weeks, 3 months, 6 months, 9 months, 12 months, etc.
Babies going through a transition have difficulty with eating and sleeping. This could be teething, rolling over, being able to see better, etc.
Babies pick up on stress. You are internally stressing about going back to work, dealing with a frustrating situation, and having mommy guilt. All valid.
Babies are more colicky (sp?) around this age.
Mommy guilt. UGH!!!! Guess what? Being a full time care giver of another person is EXHAUSTING!!!! You are allowed to vent, complain, and ask for help. We all get to complain about our job from time to time, right? It doesn't mean you want to quit or in this case that you love your child any less. Really.
My advice? Do what you have to to get through. Baby in the swing? Perfect! Baby is sleeping through the night and in a crib!?!?!? SCORE!!! (My youngest didn't sleep through the night for her first 18 months!) Ask for help! Call your mom to come visit and help. Ask hubby to step up a bit more. Schedule yourself some away time once a week until you start work. I know you are EBF'ing, but if you are going to go to work soon, are you going to be able to keep doing that? If not, it's time to start introducing the bottle. You are still giving baby your milk, and even if you weren't you aren't harming her. Ya, know?
I went through 6 years of infertility before my first. I cried a lot when I heard moms complain about their kids. I swore I'd never do that. Well guess what? I vent like every other normal parent. Do I love my kids? With every fiber of my being. I will not take them for granted, but they can drive me batty from time to time. And, I'm not always the happiest person from hour to hour, but I am overall extremely happy with my kids and wouldn't change it for the world!
Best of luck, mama. It does get better!