Pregnancy scare (please help)

Early last July, I had sex with a guy and we used protection. Although we started and finished with the condom, my anxious self got paranoid that some of the cum may have leaked out. Two days afterwards, I told Plan B and got my period a few days later (from the plan B). 4 weeks later, my period is a few days late. I'm getting extremely nervous because I have no PMS symptoms at all. My period isnt always regular, although it has been for the past few months. I also have switched to a vegan diet (which is supposed to lessen your period) and have been working out more (which could all affect my period). Should I be worried or is my period just late? Like I said, we had protected sex and he did not seem paranoid about the condom until I brought it up. My stomach also is kinda bigger now but it's probably just fat (lol). I'm entering college TOMORROW so I really want to be able to relax! Any advice would be great, thank you