How to be strong?

I officially ended things with my guy, but before I ended everything I let it all out, I brought up the pictures I've been seeing of him and another girl and I told him how I was in love with him, but I never heard anything back. This hurts so much, I haven't stopped crying and what hurts the most is he obviously doesn't care even though he use to tell me he did, this is my first real heart break, how do I be strong and when does this go away??