Piglet
Infertility is awful whenever it strikes for whatever reason. You have every sympathy, and you are defo not being unreasonable.
Actually I found secondary IF probably worse than primary for a couple of reasons. With primary IF you can avoid children/pg people more easily but with secondary you are more exposed to pg announcements/women at playgroups/friends/family. Yes, all our friends had 2 or more during our ttc time. Also, whilst ttc#2 I felt I knew more what I was missing - I hadnt really known how gorgeous babies were when we were trying before and how much I LOVED being a mummy and wanted to be a mummy to more but couldnt. I felt excluded from 'normal' womanhood because I couldnt get pg.
We spend 2 yrs ttc for DD and had 3 iui and 2ivf with no pg (although unexplained IF), we had to have a break and got pg naturally by a complete miracle. Then spent 3.5yrs ttc DS and with all the intervention possible - more ivf and iui. It had horrendous consequences financially (increased our mortgage etc) and relationshipwise. Finally we got DS with icsi on our final cycle. He was born extreemly prematurely and it was very scary. Thankfully now he is doing really well, and we are VERY proud of both of them.
Wierdly (and wonderfully) I am pg with DC3 having got pg naturally just after stopping breast feeding. I am anxious given our history but am very grateful to be in this position - only in my dreams! Our ttc journey has changed our relationship irrevocably - some good some bad. We have not had a 'normal' (ie leisure) sex life for 8 years.
I wish you luck, and try to take every day/month individually. I would encourage you to both be checked out (and not wait too long), but bear in mind that GPs are not always experienced/sensitive in dealing with IF. It is v hard to do but try to believe it will happen eventually.
I would recommend TCOYF by Toni Weschler and another book:
www.amazon.co.uk/Baby-Making-Bible-enhance-fertility-pregnant/dp/1905744560/ref=sr_1_1?ie=UTF8&s=books&qid=1259619262&sr=8-1
Good luck and I hope to hear a happy story soon!