help please

so I haven’t gotten my period yet, I don’t have sex I’m a virgin but I do have a boyfriend me and him kissed as in french kissed I have gotten baby cramps recently but it wasn’t major. this <a href="">period app</a> is telling me my period is 3 days late and idk if it’s just messed up but all I did was kiss him mouth to mouth, he did try touching my thigh but I didn’t let him. any help please?! I know I’m not pregnant but idk why this app is saying that I’m 3 days late, it isn’t the first time it’s done this!