So one night during sex the condom broke. My girlfriend was taking birth control also and still is to this day but just to be safe we got the morning after pill the next morning after the night of sex. But now 2 weeks later she had her period but she said it was way different from her regular period. She said the first day was light and so was the 2nd day but then the 3rd day was heavy like usual but then it stopped and that was the end of her period. During her period however she usually does not experience painful cramps but this time she was enduring some pain. Also her breast have enlarged slightly and are tender and sore. She also has been complaining that her back hurts and has been eating more than usual. Could she be pregnant? Or could this be from the morning after pill? She also just recently started working out.

Could she be pregnant, yes no birth control is 100 percent effective.

Most likely this is from the morning after pill, it will have many side effects.