EXTREME abdominal pain help!!!

Destynee • PCOS • 2 natural born • pregnant with our letrozole baby🤍
I'm having some extreme on and off upper abdominal pain around my sternum and cramping also feeling super sick and nauseous. I don't know what it has to do with 
I haven't tested today but I did yesterday and it was a BFN. I'm 15dpo. What do y'all think this is? I hope it's nothing serious