What Causes Frequent Urination After Having Sex While HPT Is Negative?

Hey, i have a question.

The story is very simple, me and my gf had risky intimate contact and we were scared that we could have gotten her pregnant, she had a pregnancy after 14 days and it came negative, and after that she had her period on time as normal. But she still has the symptoms that can be related to pregnancy her tummy and chest hurts a often, she has a slight increase in weight and she needs to pee often. I was wondering if there is any chance that she could still be pregnant, if not then maybe you could suggest what it may be.

Thank you