Ok I need help Im confused?

I read somewhere that u can use an ovulation prediction kit to but not take a place of a pregnancy test. Well just a lil bit ago just to see because I only had 1 pregnancy test and was waiting to use it once I was 3 days late on AF. Today is the day I was suppose to start AF. Well I know its only the am but af still isn't here so that is why i tried the opk. Anyways since Sunday I have been hungry more than normal, my saliva glands are in overdrive, cramping for a week, and lightheaded and weak. On the opk the test line showed up but it wasn't as dark as the control line but u can definitely see it. Im gonna test with the hpt in the am with fmu but I just wanna get some opinions . Thanks in advance.