I had unprotected sex on the 18th of September with my boyfriend. The overall process took about thirty seconds, and he did not climax. However, there may have been some pre ejaculate involved, and he is uncertain about whether or not he had cleared his urethra from the night before and the day we had sex. I took emergency contraceptive pills (in two doses of levonorgestrel) two days after, on the 20th. The day after, he pulled out again and did not climax inside me, and I took another dose of EC, same as before. I realize they are not to be used as regular birth control, but condoms were not available. I feel that my decision was very irrational, very regrettable, and could lead to very...messy complications if this led to pregnancy. My last period began on the 2nd of September, and I am looking forward to it like no other.
Also, I currently have a throat infection accompanied by a painful cough, and I am taking antibiotics, Tessalon, and Sudafed. Could this have any effect pertaining to my situation? The coughs are quite strong, and I have the urge to pee every so often either because of the cough, drinking water with my pills, or..perhaps it's a sign of pregnancy.

Questions:
What are my chances of becoming pregnant?
How could my menstrual cycle change as a result of taking the EC pills?

Please and thank you! I am really starting to worry, as EC is usually supposed to induce menstruation earlier than expected.