What can i do to control myself.?

Threre is this person that i really like i just see this person in the public bus. But i havent seen this person for five days and today i saw the person. I dont know why but now that i am in school i have been feeling very nervious just by thinking of this person. when i saw this person on the bus if i look at that person i would my head would kinda shake and i will get very nervious . even know in school when i am writing my hands sake a little. i even have to rub my chest in order to control this. i feel also kinda jumpe today. I cant even think stright and i am not eving seeing that person. What is this please help me co trol myself. I can understand if i acted like this when i was in the bus because the person that i like was right threr. but know i am in school and thsat person is not there. But i have been as as said been very jumppy and nervious even when i write my hands shake and i have to take a brake to rub my chest and control my self. Help me please what can i do to cont