Nerdy, I interpret a faint line on the OPK as an indication that ovulation is on its way as it shows that LH levels are on the way up. So I look upon that as the opening of the fertile window and it's probably advise able to get some swimmers lurking up there just in case.
Watery cervical mucus is an indicator that it's peak shagging week as well, so your rush of dampness in the chemist could be linked to the gradually increasing LH levels that the OPK is starting to pick up. I'd expect a positive OPK in the next day or so. Apparently you ovulate 12-36 hours after the LH surge and it's best to have the swimmers in there ready to hit on the egg as son as it's released. Hence a positive OPK is the signal to start DTD, but DTD prior to detecting the LH surge is often productive, given that sperm can loiter in the Fallopian tube for up to 5 days.
Re 'feeling' ovulation. I sometimes think I can and often get a sharp pain in my left hand side (never the right). But it doesn't always align to other symptoms. Also, I think the longer you TTC the more attuned to every change in your body through out your cycle you become and can start symptom spotting for ovulation as much as for pregnancy, with the same mixed results!
Overanxious the cough medicine you need to try is anything containing the ingredient "guaifenesin". It is an expectorant, so most cough medicine for chesty coughs should work, but check the ingredient list first. The brand that I have had recommended is Robitussin, but any expectorant should work. Which reminds me, time to pop to Boots as I am mid ovulation at the moment and haven't got any (recommended dosage is 2-3 times a day, starting a few days before ovulation, I may have left it too late now).
Commiserations to all those in the hut with AF. It is just unmitigated crapness. But when you feel ready to emerge from the gloom, you have a shinny new cycle awaiting you, full of possibilities; arm yourself with your temp chart, OPKs, CBFM, cough medicine, pineapple, saucy novels, impractical shoes and whatever combination of aids to conception you feel appropriate (oh, and DH / DP might be necessary as well!) and keep everything crossed (except your legs) that this might well be our bloody lucky month!! Good luck everyone. 