CM - the difference..?!

Jade
It's going to sound silly, but I pretty much know everything about TTC. I think I know about CM, but I'm not sure. Lol, that didn't even make sense. I know that CM is a pretty important part in TTC, hence why I want to know more. 
Basically (tmi) I sometimes - not every month - get a blob on the tissue when I wipe that looks like jelly - very stretchy and stringy. Is this fertile CM? Then sometimes, in all cycles, I get like a glistening on the tissue when I wipe. Apart from that I'm pretty dry. I don't get milky coloured CM or anything like that. I was wondering what the stages are? And how I know I'm ovulating by my CM? Because 9 times out of ten, when I do ovulation tests religiously throughout the month I don't get a positive!