really scared

so my period hasn’t came it was supposed to come on the 15th and it’s now the 18th and i took a test test and it came back negative but i still don’t know what to do, idk if i should trust that test or not, and back in april last year this same thing happened, after 5 days my period came and i never took a test or anything, i’m just really hoping it’ll come tmr morning but i’m feeling hopeless