Implantation?

My girlfriend and I had unprotected about a month ago. Afterward, as a precaution, we used the morning after pill. It made her very sick. About a week after the act, she had a very small amount of reddish-brown bleeding. When she went to a doctor for an unrelated issue about a couple days later she asked about it. The doctor said it could be due to the large amounts of hormone she ingested, which was way more than her body weight needed. We've also heard that the bleeding could mean that implantation had occured. We want to know whether that meant that she is actually pregnant or not. Is a small amount of bleeding about a week after mean she is definetly pregnant? Any advice would be appreciated!