Anxiety

A few Sunday's ago I had a mental break. Ever since then I haven't felt the same.
I feel like I'm spening more and more time alone and that makes me feel sad.  I feel like I'm drowning and no one can save me. I don't know what to do about it.
I think part of the reason I'm feeling this way is I feel lime I'm losing my sister. I hardly ever see her and I don't even know whats happening in her life any more. She doesn't confide in me like she used to, and honestly I don't think I know her anymore.  It makes me sad that she won't tell me stuff thats going on her life. Like I didn't know about her crush at work until way later when my mom told me. My sister insisted she told me about it, but all she said about him was that she though he was cute. I knew nothing else. I didn't even know she had a date on friday until my mom told me she did.
I don't even know my sister anymore and that makes me sad.
But whatever.  I'm floating away from everyone and no one seems to even notice. 
Is this what depression feels like? Maybe.
Ever since Sunday, I've been getting super anxiety and I think that its going to end up killing me.