I Had Sex On 15th August And Was Due My

I had sex on 15th august and was due my period on 20th aug but took the ellaone emergency pill the day before on 19th,ive not had my period but had spotting on and off and took lots of tests which came back negative but this morning two cheap hpt came back faint positive,is it that im pregnant or the ellaone that's causing no period n false positive?