I was totally in the same boat as you. I had some pretty amazing PPD after the birth of my son, and he had feeding difficulties as well. My second pregnancy was with twins and I was just certain with double the hormones it was going to be twice as bad after. Also, I had no idea how I was going to breastfeed twins if I had such problems with my first, a singleton.
Well, lactation first, because it plays into the second. Get in touch with a lactation consultant now. Find out how to get in touch with her after your baby is born and have her visit you in the hospital to make sure the new baby's latch is fine. Go to Babies R Us and pick up a nipple shield, just in case. If your new baby has difficulty latching onto the nipple, the shield will help you both get started on the right path. The lactation consultant will help guide you through the use of it. (It looks sort of like a cross between a sombrero and a condom. It was a Godsend to me and I would not have been able to nurse 2 of my 3 children without it.)
It is somewhat of a Catch-22 that if you are able to breastfeed, it will release calming chemicals and help with the anxiety, but if you have difficulties it simply contributes to the emotional roller coaster.
Also, for combatting PPD, get outside for fresh air and sunshine as much as you can. A little exercise can release endorphins and the Vitamin D is essential for your health and your milk. A daily dose of medicinal chocolate was also helpful to me. Not so much as to be an issue, but enough to say "I'm treating myself for a good day of mothering" and the chemicals in chocolate are also a fairly natural way to boost a mood.
As ever, having someone on speed dial you can call to vent to is important as is getting time to do things like shower and brush your hair. Even if you feel guilty for leaving your newborn in a crib so you can take a shower, think of it this way, "If Mommy ain't happy, ain't no one happy." So really, it's in baby's best interest. :-)
Good luck to you.