Very upset and lost right now ..no surge detected

I've been testing since Saturday and according to my app I was supposed to ovulate anywhere between wed-friday but it's Thursday and no positive kit yet....im really upset and stressed out because last month the generic strips I got did not work at all...I have a regular cycle and have been ovulating every month within that time frame my app says....has anyone ovulated a little later? I'm really worried it may be me and I may have some issues now that I'm 31