Unsure if pregnant

so I'm 3 days late to my period (normally like clockwork) and done a few tests. Some came back negative and some came back with an ever so faint line that I can see but my partner can't. I feel like I'm going crazy?! I was on the pill but missed one by accident a couple of weeks ago as well as being ill. I don't know what to do because I feel stupid if I aren't pregnant but I can tell something isn't right!