When can I test.

Mystery
So me and my fiance have been trying for a baby, and we started trying a year ago, and after all the negative test and the disappointment of waking up to a period. I think we may have actually got it this time. I'm 4 days late for my period now. And I'm the girl who's always testing to early. And I really don't know when's the right Time to test. And I'm kinda scared to test because of the disappointment in the past. Any advice?