Well, it sounds to me like your girlfriend might just have experienced some spotting which is something that can sometimes happen. It could have been due to something as simple as ovulation for example.
You said you used condoms. If you used a condom for all genital contact and it did not tear or break, then your partner didn't have any pregnancy risk and therefore can't be pregnant.
There are a lot of reasons why your partner might feel more hungry lately and this generally doesn't have anything to do with pregnancy, especially this early in the game.
If you used a condom correctly, you have only a very, very small pregnancy risk.
There are very few pregnancy symptoms would show up so soon after intercourse. "Spotting," or light discharge of blood from the vagina, can happen because of a variety of reasons: for example, beginning hormonal birth control, or having a small tear.
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