OK typed a huge complicated post, then edited: welcome to the short version!

I am 1.8m tall, my medically “normal” weight is between 60-81kg, but ideally I should be 65-70kg. I am currently 62kg (BMI 19.1) and have lost 2kg in the last 2 weeks. I’ve been about 64-66 for the last 9 months or so as getting to this weight was one of the pre-requisites of TTCing, though DH pushed the goalposts back after I reached that weight. I was married in September 2004 and came off the Pill in August 2005. When I married, I weighed 60kg and my size 6 wedding dress was very roomy even after a 4-course meal (and very tight this Christmas when I was showing it off to cousins who couldn’t make the day). Once married, I struggled to put on the extra 5kg and that took me 7 months (yes, I do know I’m an evil *****). I’ve kept that on for almost 10 months and then have started losing it again. This is my 5th post-Pill cycle so don’t think the weight fluctuations are due to hormoney things, though I’m meant to be ovulating in a week or so if my cycles are staying at 6 weeks. People are starting to comment about how much I’ve lost.

One small problem is that I feel very fat over 64kg and DH really prefers me to be at this weight (well, I get a lot more complements) even though he encouraged me to keep the weight on when he put back the TTC start date as it’s technically healthier for me. I was only that weight with pregnancy in mind, so am happy at this weight, but want to TTC and don’t want to talk DH round only to wait another 6 months because I’m too thin and need to up the weight. I’ve got a feeling he’s going to stick to his guns though and we’ll wait until September-October 2007.

So, questions:
How underweight is too underweight to have a healthy pregnancy and to ovulate?
Should I just bite the bullet and put the weight on (and how)?
If I talk DH round to TTCing this cycle, is there any chance of getting pg so should I leave it until next?
Should I just leave off any conscious weight changes until next Easter, when I have 6 months-ish to fiddle with my weight before we start to TTC? If so, what do I do if DH decides to go for it this year?

What does everyone think?