Possible miscarriage???

Hey ladies so I need some advice....I had unprotected sex and my boyfriend came in me. Less than an hour later I took a Plan B pill. I am now 31 days late on my period and I have been having some symptoms of early pregnancy HOWEVER I have taken two pregnancy tests and they BOTH came back negative. But for the past three days Ive had intense cramping and some spotting. When I got home today, this happened. Is this some kind of “massive clot” or could this be me having a miscarriage?! PLEASE HELP! 😭😔