Having had a baby at 24wks due to suspected IC, I can vouch for the fact that an IC dilates relatively silently.
On reflection, i did have loads of vaginal pressure from about 22wks, and my pregnancy discharge did increase significantly the week before i discovered my membranes were bulging thru my cervix. Also, I did have some mild backache, but this was at the eleventh hour when everything had already changed.
All that said, I had copious amounts of discharge in my first pregnancy, with lots of aches and pains and vaginal pressure - my son delivered at term.
The point about IC is that you do not have regular painful contractions. The twinges I felt at 23wks were as a result of an already dilated cervix, which had done so without any obvious signs.
Please try not to worry about IC. It is extremely rare, and aches and pains in pregnancy are completely normal. I am currently pregnant with twins, have a cervical stitch in place as a precaution, and have been plagued by constant pressure, aches, BH contractions and scary back aches. So far none have affected my cervix, and appear to be a normal part of carrying twins/having stitch in place.
Good luck, and relax hun x