28 day cycles. had unprotected sex twice during most fertile days. period is now four days late. minor cramping, no bleeding. neg pregnant test 2 days ago?

Late period: Probably not pregnant if the office test was negative. If you feel fine, then see what happens over the next two weeks. Get checked if you still aren't sure by then.

Neg pregnancy test: I suggest repeating the test in 2 days. If still negative i suggest that you have a blood test. The concern with a repeat negative urine test is a tubal pregnancy.