Delayed menstruation

I missed my period for 4 days and I'm getting worried a lot. recently I went to a parenthood plan center and when I was there they gave me STD and pregnancy test which came out to be negative. I guessed the reason why I'm delayed is because stress, but...

how long do I have to wait? the longer I wait the more I get worried.

Chill buddy... 4 days delay is normal... but I think you shud worry after 4or 5 days more.. then go to a doctor...

If you are that worried see your doctor, although it's normal to miss a period when you are super stressed, you have already been told you are not pregnant, I would just wait and see if your period even comes this month, if not then wait and see if it comes next month.

I'd give it till the end of the week then take another pregnancy test.

well if youve had unprotected sex, then theres a possibility that your pregnant
and the affectivness of the tests depend on how long you waited after having sex
you can take a pregnancy test
or get a blood test at the doctors for a more accurate result
other reasons for missing a period are
stress
not eating properly/avoiding food/eating disorders
and over exerscising