Wow, I thought it would be easier to tell than this...
Background: I'm 40+4 today. Have had a few false contractions/strong Braxton-Hicks a few days ago, nothing since late Tue. Went in for a sweep yesterday but the baby's head was pushing the cervix so far back they couldn't reach it, not even enough to tell if I was dilated at all. I've also been having consistent problems with incontinence and not completely emptying my bladder, since way early in pregnancy.
So, this morning (after waking up really late 
), after I went to the loo, I plopped down on the sofa and suddenly felt a gush. I went straight back to the loo, figuring I hadn't succeeded in emptying my bladder -- more wee came out, as typical. I changed my pad, but noticed that there seemed to be more liquid than I'd expect. But I had slept really late and maybe my bladder was really full.
Sat back down, after half an hour, felt more trickles. Went back to loo, had a lot more wee (and haven't had much to drink yet). Also noticed thick, clear mucus from vagina when wiping. Since then, I feel like I'm being a bit more incontinent than normal, and was recently outside hanging out the washing and coughed and kept getting gushes with each. But I've been having trouble with leaking wee with coughs -- even if I hold my pelvic floor tight.
I tried smelling the pad, but it is useless -- I have cats, and human wee just doesn't smell strong enough to me (I know as back in week 16 I was having a fluid-or-wee issue and actually weed on a pad to test, and couldn't smell urine).
Since then, it basically feels not so different from my incontinence issues, but just more so. And if the mucus was my plug, wouldn't that have come before the waters, not sort of in the middle? Is this my waters breaking or not?