Having Sex Offputs Period

So I've recently had sex for the first time and we used a condom and were really safe and everything. I didn't think anything of it until I sneezed and got cramps and when i looked it up it was all people who were pregnant had that symptom. I'm sure I'm not pregnant but I was wondering when you guys had sex, How long did it offput your period?? I haven't had mine for 3 days