Calm down. There are way more things that could cause a missed period than being pregnant, you're not even late yet
Sometimes you won't be regular, as long as you get one a month you're usually okay and you're panicking right at the start of the month. Sometimes I can go months not having one at all due to stress or other external factors. Even things like not eating enough could cause you to skip a month so stop, breathe and don't panic.