Clear Liquid

Hey, sorry if this is really disgusting to post but I’m slightly confused.

I have started using the cup and until now it hasn’t really collected anything substantial from my period, I’ve not bled a lot.

Tonight I took my cup out and a ton of liquid fell out. However, it wasn’t blood, it was just clear watery liquid. Enough to fill the cup!

I’ve never experienced this as I was a die hard tampon user until now, what is this discharge? Is it just my body being fertile? Sorry if it sounds stupid! Just not sure! Any help is appreciated :)