Is it normal to be sad about some boy?

I had secretly liked a boy who was my clmate in my country.(i'm now in US, and i'm not american) a year ago, i moved here(US), and i'm not able to see him anymore. it's not like we had a relationship, he probably never knew i liked him. i was 14 when i started to like him, and after 3 months of secretly liking him, i came here in US. now i'm 16 and i sometimes think about him and be sad. i even cried yesterday. what i'm asking is, is it normal to be crying over some boy who i secretly liked? is it stupid or immature? i never liked a boy before, and he's the first boy who made me feel that strange feeling. i never felt like that before. it was so special. and now when i think of him, i feel heartache or sth. seriously. i never felt like this before i met him. what is this feeling? and is it normal to cry about this? it's been a year and a month or so since i last saw him.