I joined 3FC just to say you're not alone! I'm also due in March too
I've been using the recipes etc on this site for a couple of years but have never bothered with the forum but I could have written your post myself.
I lost 84lbs after I had my son 3 years ago. I was already obese and finally got to a healthy weight and now the very idea of gaining is terrifying!
I gained about 44lbs when I was pregnant with DS and as I was already overweight that just tipped me over the edge. After I had him I dieted for over a year to drop all that weight and now that I'm pregnant again the fact that my body demands more food and that I should be gaining almost sends me into a panic attack.
I was pretty obsessive too, to the degree that I'm pretty sure I only narrowly avoided an eating disorder. The only thing that pulled me out of it was the fact that I went away from home for work for three months nearly 2 years ago and had no control over what went into my food.
I spiraled out of control by comfort eating and gained quite a bit so that by the time I got home I was about 15lbs heavier than when I left. I haven't been happy with my weight even briefly since then because I couldn't get back to my goal weight of 143lbs.
And now that I'm pregnant again, well you can imagine the fears resurfacing and the distress I'm feeling at my body being so... Rotund.
It's not healthy I know, but I can't help myself! I know all about nutrition and fitness. I'm also very aware that I need to gain a healthy amount of weight and so far I've managed to stick to being in between the minimum and maximum gain amount recommended for me. But it doesn't help when everyone keeps saying to me "You're supposed to get fat!". People don't realise how that makes me feel. When I look in the mirror I see a huge belly and can't help but think that there's no way I should be that big. At least I look pregnant this time instead of just fat :/
I'm lucky I think in that I decided at the beginning of this pregnancy that I would stick in between the minimum and maximum 'healthy' gain amounts and so far I've achieved that with sensible eating and not snacking on junk. But I do know exactly how you feel, with perhaps the added incentive of having to be careful that I don't slip back into obsessive compulsive and unhealthy eating behaviours. It's a struggle but I'm getting there