My period is 4 days late?!

I’ve taken two pregnancy tests that both came back negative and I’m starting to get worried. My period has never been this late, though recently it has been a bit irregular. In the past year I’ve had 26 day cycles and up to 32 day cycles. Sometimes my period will last three days or even up to seven now with cramps so bad I’ve had to call into work. For years prior to this one, my periods were always 30 days apart and always lasted 5 days with minimal cramping. I haven’t had any change in sexual partners as I’ve been with my boyfriend for over a year now. I’m not on birth control and I never have been. Maybe it’s stress but either way I’m worried and I’m curious to see if anyone else has experienced what I’m going through and could help me figure out what’s going on with my body!