I was sick this morning and it was white foam? i had sex 3 weeks ago but im on the pill, pregnant?

i had sex 3 weeks ago, i am on the pill and my ex did *** in me but i werent taking my pill dead on time like i normally do due to having lots of late nights, past week ive been feeling sick but ive not actually been sick and this morning i felt light headed and then i was sick but it was like a white foamy sick? i dont know if im pregnant or not help?