Beths Fishy Friends

Hi, today I bought a betta from petstock and I am worried there is something wrong with my fish because he keeps on opening his mouth really wide every couple of mins. Is there something wrong with him? I have tons of Bettas and experience beforehand but nothing like this has ever happened to my fish. If someone could get back to me ASAP that would be amazing? Thanks, Beth p.s if I could insert a picture of him doing as said I would but my account is currently not letting me?