what is this feeling?

Finals start tomorrow. I have a major presentation I'm really nervous about. This guy is playing with my heart like a guitar. My sister is so self-absorbed she makes me want to claw her eyes out. Her boyfriend is so emotional I think he's PMSing. My dad won't tell me how he is or what's going on, and he's focusing on my sister (because she needs more attention...). My mom has been bitchy lately (shes admitted that), and seems insensitive about all this stress I've been under, even though it made me have the worst anxiety attack of my life.
And to top it off, she came home at like 2 3o, for her lunch break, me, my sister Ashley, and her boyfriend Cory were home. "Ashley, Cory. Take the dog for a walk". "Okay" they say.
she comes home at 8 "Did Ashley and Cory take the dog for a walk?"
I thought for a second, I had been in my room all day studying. I didn't here them leave until she brought him home. "no". I say
she brings me out into the kitchen.
"this is bullshit. I'm telling you, and I will tell Ashley, too. I'm looking into giving Stevie (our dog) to someone. YOU guys wanted a puppy. well you got what you wanted. now why am I the one thats fucking taking care of her? and look at this, all this shit. I just cleaned the kitchen. You knew the dog didn't get a walk, why didn't you take her?"
"I've been studying all day"
"Lisa, it takes fucking 10 minutes to walk the dog".
"Well, I thought Ashley and Cory were going to give her one"
"That's right Lisa, pass the blame."
I blankly look at her, then walk away.

I know I should be crying right now, and 10% wants to just start blubbering. But, there is this feeling I have that I haven't felt in such a long time. It's almost like a "just fuck it" feeling. I feel numb. Like there is a hole through my chest and no matter what I do it will always be there. I will never get away from the pain. It's like I'm shutting down, nothing can phase me now. That scares me.