What are the chances of bein pregnant?

Hi there, 2weeks ago i took the morn after pill after condom splitting with bf, altho i did take late2 and a half days after , then my started to get really sore last week, although i was due on i neva really get sore , anyway I 'came on' lightly sun 2nd dec but b4 this i was getting thoughts that i was preg n waking up through the night n goin 'im preg' but i came on then 2day(mon 3rd dec) i was still light on period n im usually really heavy so i took a hpt n it came out positive but now later on in the evening my period pains r getting worse in the back n more blood i think is coming out so im wondering could the test be wrong? i have been taking epherdrine for when i workout could this affect the result of my test-ephedrine speeds up the heart rate n gives u more energy it is actually banned coz it gives amphetamine like effects but it is not a drug-also if i am preg i am now worried i hve been taking this whilst preg4 2weeks!any advice no stupid remarks pl