help if you please

hi, the last day i had my period was on the 17th and i had unsafe sex with my boyfriend on the 22th, and i am sure he did not came inside me but still he didnt use a condom,, today i got worried, i was thiking of it and i realized how stupid i am? i might get pragnant, yes or no? what can i do? how can i prevent this now! is it to late? is it possible that i might get pragnant? its only 5 days but i dont know am worried and i cannot sleep! any one please help.. am only 18 and i dont know what to do.. now..
please help me..