<human>: Provide a brief overview of the text.

I'm 19 y/o male, and I've been with my current girlfriend (20) for a year and a half. Yesterday, we were out Christmas shopping at the mall. She went to order us some Chinese food, and I went to find us a place to set our bags while we ate. Walking around, searching for a table, my eyes met my previous girlfriend(~2-2 1/2 years, longest relationship I've been in). 

My ex was only my ex, to my knowledge, because she was cutting all her ties and moving across the country to live with some extended family to attend college. I ran into her in our hometown mall, talking to her same old friends. 

I didn't even speak. I was paralyzed. I dropped my bags, and froze. I didn't know what to do. So many emotions coursed through my body, I had no idea what i'd say even if I had a million years to think about it. So I didn't. I cut my eyes away quickly, double-taking to be sure it was her, and it was.

Since then, I've felt empty. I've genuinely felt nothing. I had my apathy behind the excuse that I was sick for the past few days, but it's going to wear off eventually.

 I haven't spoken to my current girlfriend about it, or anyone for that matter,and I'm terrified to. What do I say, if anything at all? How do I approach it, and what do I make of all of it?
<bot>: I ran into my ex at the mall while me and my gf were off doing our own things, and she doesn't know about it yet. Do I tell her? How do I tell her? What do I say?