I am vry regular with my cycles this time its been 3 days no period,taken test it came negative,am studying wondering if this strees can lead to delay ,

Not surprised you got a negative being its only three days late.

You are aware you really need to be two weeks late or you are wasting your money, and still might get false negatives up until 4 weeks late... and that assumes you are taking them at the right time of day... meaning ONLY in the morning the FIRST time you pee, not when the mood strikes.

You're testing too soon. You need to wait until you are at least two weeks late, then test using first morning urine. When you're pregnant, your body produces a pregnancy hormone that builds up in those first few weeks. Until it's present in adequate quantity, you will get a negative result, and thus the need to wait a couple of weeks.