I always had irregular period cycles but my average cycle is 35 days. my period is now about 4 weeks late (the latest it has ever been), i took a pregnancy test and the results was negative. am i pregnant?

Tests are accurate: Home pregnancy tests are very accurate and not affected by foods, coffee, common illnesses, sexually transmitted diseases, or medications. A correctly done urine test gives a reliable result by 3 weeks after sex (3 weeks after when conception might have occurred) or 1 week after missing a period. If done sooner, a positive result is likely real but a negative result may be due to testing too soon.