I could cum !!

So normally I only mainly cum with my clit and I have one every single time me and my Fiance have sex! But last night I would literally about to cum and it just wasn’t happening!! So then I tried doing it myself and the same happened again and my partner and I tried TWICE more😂😂 and it was at the tip of my tongue and it just went?! This NEVER happens!! Does anyone know what this could be???