Since you had unprotected sex this cycle, pregnancy is one reason for a late period, especially with the mild cramps and light spotting you're describing. A normal shift in your cycle from stress, travel, or timing is also common and doesn't mean anything is wrong.
Next Steps
Take a home urine
pregnancy test today. An early negative result doesn't fully rule it out, so repeat it in 3 to 4 days if your period still hasn't started. If it comes back positive or the cramps worsen, please see your gynaecologist, who will rule out a miscarriage or an ectopic pregnancy.
Health Tips
Go in sooner if the cramps turn severe, the bleeding becomes heavy, or you feel dizzy or faint.