I tried mucinex ( guaifenesin only) this cycle, from cd 13 until I was certain I had o'd, yesterday. I took 600 mg twice a day. It made a huge difference for me, so I thought I'd report back : )
It doesn't give you more cm, but thins out what you have. I ended up with tons of watery cm, and a tiny bit of ew. Normally, I get a bit more ew, but very little watery. I definitely felt more fertile.
We'll see what happens.
Sunday