baker - step away from the internet! If you cant resist please please use reputable sites such as patient.co.uk, or NHS choices.
What are you worried about being "wrong"? Firstly let me reassure that being on the pill definitely does not affect your fertility in the long term. Yes, it can take a few months for your cycles to settle down when you stop taking it, but it doesn't reduce your fertility. Also IBS is a pain, but doesnt affect your fertility.
Periods are a variable affair - light, heavy, long, short (just like people!). If you are having a regular monthly cycle roughly 21-35 days, then that is absolutely normal. Very irregular bleeding, passing lots of clots during your period, having cycles much shorter than 21 or longer than 35 days, bleeding midcycle, or bleeding/pain after sex can be markers something is "wrong" and is worth going to see your GP about.
Your cervix can be very sensitive - why do you think dilating it during childbirth is so painful! Different women have differently sensitive cervixes, and poeple with IBS tend to be very aware/sensitive of their "insides". If touching your cervix is really very painful (throughout your cycle), and causes you lots of pelvic pain, (or you get deep pelvic pain on sex) that is also worth going to see your GP about as it may be a sign of Pelvic inflammatory disease. It just being a bit sensitive is normal though (it wasnt designed to be poked!)
And remember. The AVERAGE time it takes for a woman to get pregnant if having regular, unprotected SI is 5 months. That means half of normal people take longer than that. Around 1 in 7 couples will not be pregnant at 1 year, but more than half of them are pregnant by 2 years (ie have no "problems" with their fertility).
Hope that helps :) I know its really hard to be rational when in the 2ww and loads of hormones are sloshing around to try and make you a bit paranoid - we've all been there!