idk ?

I don't know what's wrong with me I was having my regular periods back after being off birth control . An my periods started to flow back normally for the past 6 months . But now all of a sudden I'm three days late . I want to get pregnant but not sure if I am because being three days late I believe is normal . I have a headache in which I just took medicine . An I'm bloated and I'm constipated . I don't what's going and this headache is a