EKG can be false negative, it happens to quite some people. X-ray doens't show the blockage of artery, a CTA（coronary computed tomography angiogram）can show the blockage of your artery. The only blood test to diagnose heart attack is cardiac troponin-I(cTNI), it takes at least 4-6 hours for the protein to go into the blood after a heart attack. If your blood test didn't include cardiac troponin-I, the blood test almost doesn't say anything.
So if you feel chest pain, you get cTNI test, that's the way to confirm a heart attack. And, you may get a CTA scan, to find out the blockage of your artery. It's a common heart scan.