Ugh, here it is again, showing it's ugly head...depression!
Awww, it does sound like you need to talk to the doc. I know -- taking anything during pregnancy is scary. I was afraid to take my m/s pill and only did so because I was soooo nauseous and had too much to do at work to be feeling poorly. I even suffer through a headache as long as I can before taking something (which is probably dumb since it only gets worse). So I understand your feeling here, but if your doc and other docs are telling you it is safe, then maybe you can put your trust in them and see if you can adjust, even just slightly. Pregnancy is just too hard on a gal to add depression to it.
I've also heard that the UV in tanning beds is used to help treat SAD, but I'm not entirely sure doctors advise that while pregnant (but not like you'd go everyday and get tanorexic or anything)... so you should inquire about that. If 10 minutes a week even could boost you, that would be incredible.
Poor bug. :(
Honestly, since it doesn't cook your insides when you're not pregnant, it stands to reason that the UV lights themselves won't hurt the baby. I think the bigger concern is getting overheated. We're not supposed to take really hot baths or go dipping into hot tubs, so that, I think, is the bigger concern here. Well that and skin cancer, of course. (And I suppose that's quite the biggie.)
I'm not entirely certain how much time exposed to UV rays is necessary for effective treatment for SAD (or even if it could help you, for that matter) but if just a few minutes a week would help, then I think the risk of overheating would be minimal. But that's just going off my experience when I tanned. The first few minutes weren't hot at all, especially when in a good bed -- the kind with a lot of fans and/or high-speed fans. But that was me -- I'm sure someone else's experience could be different.
But, I would NEVER consider doing it without my doctor's ok. I think a convo with the doc would be beneficial, but of course if you were remotely worried about it, it wouldn't be worth it to try. You don't need one more thing to be worried about at this time.
Ideally what will happen is you find that the light box is going to work for you and you won't even need to think about other alternatives. That's what I'm hoping for you.