Hi,
I'm sorry this has caused you so much stress :(
The stress and anxiety you are experiencing isn't uncommon; many women go through the same feelings you are having, after their first time. Try not to worry yourself too much; it will only cause you to be more stressed out and panicky. It's unlikely that you have become pregnant on the heaviest day of your period (although it's not impossible), but because you also used a condom during sex I highly doubt that you are pregnant. The best way to be absolutely certain about being pregnant or not, is to take a pregnancy test... Maybe your stress is also being contributed by some regret about having sex earlier than you had planned or expected? It's okay to feel some disappointment, but try not to beat yourself up because of it. Keep in mind that life doesn't always go as planned, but at least now you know what to expect from your next experience and how to be better prepared for it...
In regard to the bleeding and pain right after sex for the first time; it's normal for some women to have light bleeding or spotting from 3 to 5 days after losing their virginity. If the bleeding and pain last longer than 5 days, you should make an appointment with your doctor for an exam. You may feel vaginal discomfort or tenderness for a few days afterward also. For the pain you can use an over the counter pain med. like Advil or Tylenol. Since you were on your period, during your first time, you probably won't notice the bleeding/spotting as much. If any pain persists for more than a week, go get checked out by your gynecologist.
Hang in There, You'll be Okay :)