Took morning after pill, pregnancy symptoms 8 days later?

My boyfriend and I had unprotected sex on June 22. He pulled out and came on my stomach, but we were afraid there could have been some inside me. To be safe, I took the morning after pill a few hours later, and 12 hours after taking the first I took the second pill. I did exactly as instructed. I did not experience any side effects after taking the pill, so I was afraid it did not work. Now, 8 days later, I'm experiencing lower back pain, very swollen/tender breasts, and a slight change in the color of my aerolas. I get my period the first week of every month. The instructions to the pill said I might get my period a week early. This did not happen. What's going on? Could I be pregnant? Thank you.