I had antenatal depression for several months during my pregnancy. I even saw a mental health nurse about it this week (bit late as I now feel totally like myself again!) who agreed that it was likely that it was a lot to do with the shock of finding out I was pregnant etc as it was totally unplanned and there are such a lot of hormones going round our bodies that we are not used to. There are several good websites so maybe have a search on google or something so you realise that you are not on your own and that what you are feeling is really quite normal. Apparently 10% of pregnant women suffer from antenatal depression and it is not just normal pregnancy blues. Is also a good idea to be a bit prepared when seeing the GP to make sure they don't fob you off!
I wasn't keen on taking tablets if possible (and luckily felt a lot better after a while so no need) but homeopathy really helped me. i know some people are sceptics but I was willing to try anything to stop the daily tears!

I hope you feel a bit brighter soon but you are def not on your own in feeling like this.