17 days late..

No period still after being almost 18 days late! I’ve taken a test and it was negative. I can’t be pregnant because I’ve been having protected sex as always, and my boyfriend has only ever ejaculated inside of me ONCE and that was ages ago! I always tell him to pull out as I’m always scared. I haven’t actually had sex for around a month! I’m not sure if it’s stress but I can’t say I have been stressing much, especially not before my period was due🤷🏽‍♀️ HELP