I Had A Sex With My Fiancy At Last Month..

I had a sex with my fiancy at last month.. after i missed my period..my period date was 13th.. and i had sex on 15th.. bt till now.. my period was not came. I checked with pregnancy meter it shows me negative.. bt is there any possbility to get pregnancy.. i dont want to b preganant now. Could u pls refer me any medicines for avoid pregnancy