becca,
i understand your guilt and it is going to be hard to get over if you choose abortion. however, like noddy said, it isn't like you are using it as a form of birth control. you made the most extreme move you could last year to not be able to have children anymore, and yet for some strange reason it didn't work (I personally would be questioning the person who did your tubal ligation to see if there is any other reason than chance it happened). You have to weigh all of your options. you had a hard delivery with complications for you child at 20, it may or may not be worse at 32.
i personally am all about the finances (being a money manager professionally i can't help it!). mr. d and i haven't had kids because we literally can't afford it yet. i take extreme measures (not as extreme as you obviously since we want kids in the future) to not get pregnant.
me personally, i would think about the baby's health prognosis (and yours for that matter) if you carry to full term. that is probably most important at this point. it may be good, it may be bad, but please, please don't beat yourself up for this, you took every precaution not to be here.
and again, i am all too familiar with cysts if you need to know anything about them
good luck.