I am on the pill but am i pregnant or not?

i am on the pill and i had sex ove 3 weeks ago, i have NOT missed one pill but i have been taking them different time during the day due to having late nights etc im really worried, for the past week i have been feeling sick and havent been sick and yesterday i was sick and it was like a white foamy type of sick? there wasnt a lot of it tbh and i know he cummed in me am i pregnant or?? ive been feeling light headed too and have been having hot and cold flushes? need help! :(