My girlfriend and I had oral sex last month. I just came into her mouth then after an hour, I kissed her then gave her a head, I was so worried last month thinking that she might get pregnant but she had her period which I think was normal

I guess it was normal because she had heavy cramps and she had to change her tampoons and it also last for 3-5 days. Now I am still worried if she's pregnant because of what I read in the internet that you can still be pregnant even if you had your period last month. I badly need an answer, does my girlfriend can still be pregnant?