I Had Sex On The 15th Of September At 2pm

I had sex on the 15th of September at 2pm I vomited at 11pm and again the next morning. I had cramps that day. I have had lighter cramps, sensitive boobs and been very hormonal since. Last night, 20th of September I started bleeding and have been since, heavy enough to need a tampon. Is this a sign of pregnancy or a sign that the morning after pill has worked?