Hey HM. As you will no doubt have seen from the flood of posts you are so not alone in experiencing this. I had a bout of debilitating, awful depression just after I found I was pregnant. We're obviously all going to have different experiences of this, but my depression lifted at about 12/13 weeks, along with the morning sickness. I put it down to hormones settling down - don't under-estimate their effect!, along with the time to adjust to the idea of pregnancy - I also have a history of depression and we depressives aren't known for our great resilience in times of change!
I am 20-odd weeks now and (the odd blip aside) feel fantastic, a bit lalalaaa, like I am being cocooned and cushioned by the same hormones that dragged me down. So, I am hoping this is good news, and that your depression might run the same course as mine.
But also you do need to follow all the good advice you have had here about contacting your GP and making damn sure they refer you properly for counselling and ADs, which are FINE in pregnancy. I am also going to go and see my GP again pre-birth to make sure they are ready to help me if I have a post-natal crash.
And of course come on the boards and talk to us as much as you need to. Good luck. Am going to post this on your other post too.