Can a change of diet ruin my cycle? (PLEASE HELP)

Jess

Okay so I'm on this new diet where I don't eat any dairy or red meat, anyways my period was scheduled 14 days ago and eve is telling me I have a 26% chance of being pregnant. But I took a pregnancy test and it was a solid negative. I'm taking a new one today. But I'm freaking out and I need some help if you guys know anything about how a diet like this can effect my period please let me know!!?