I Am Worried That I Might Be Pregenat I Had

I am worried that I might be pregenat I had my last period on the 7th Decemeber I had sex on the 9th the 16th and the 24th withdraw was the protection method I know that it is not reliable but we were very careful I suppose, the plan b pills are not traded in my country. By all means I don't want pregnancy to happen. Please help