(Slight tmi) Is my water leaking?

I’m only 28+2 weeks pregnant and I usually have discharge so I’m not usually super worried. My discharge has been kind of changing since I’ve been pregnant from more mucusy to more liquid I guess. I kind of just put it down to changing hormones. Now, why I’m concerned is, this morning I woke up to really liquid discharge. Like, liquid to the point that it was running down my buttcheeks towards my back (sorry tmi. Im just not sure how else I’d describe it) I don’t want to make an extra trip to the doctors and it turns out to be nothing but I’m worried. I’m supposed to have an ultrasound in about 2 and a half weeks, would it be dangerous to wait that long and ask to be checked then? Or should it be okay? First pregnancy so I’m a little paranoid. Thank you!