Whitney: Wow. What's the occasion?

Lana: Nothing. I just thought we'd blow off class, today. (skip school today?)

Whitney: I-I can't. I'm barely keeping ahead. (making up for the lost classes?)
Then I got to go to the store, and then run by the hospital and see my dad.

Lana: You know what? I am tired of your excuses. Ever since your dad got sick, you haven't been any fun at all.

Whitney: I'm sorry, Lana, but it's kind of a big deal.

Lana: Whatever. I feel like I'm locked in this relationship out of guilt.
(She continues with the relationship because she feels guilty?)

Whitney: Lana, what's wrong with you?

Lana: Nothing. I'm just not keeping it inside anymore. (not suppressing her feelings?)
Correct on all except 'keeping ahead':
not falling behind, as in a foot race; another expression is "keeping one's head above water".
Thanks, Philip!