It is really hard to distinguish between antenatal depression and hormones because they are inter-related. But basically if you are feeling really low and miserable and you are pregnant then you definetly should talk to your GP. It isn't you being silly at all, it is a very real problem, it isn't your fault and there is support and ways in which they should be able to help you.
Nothing you can say about this to your GP would be silly at all. If you have a nice GP then talk to them. If you have a nice midwife, talk to her. But do mention it to someone.
It is so hard when you are feeling depressed about things. I suffered from some exceptionally bad PMT for a while (hormonal because of the pill I was taking!), and I would take real issues in my relationship and blow them into something so major and dreadful I felt like the relationship should end. It was so hard because I was focusing on things that were issues, but in such a way that was so dispropotionate it made something small but real into something enormous and distructive when it should never have been.
What I'm trying to say in a long rambling way is that hormones can have a really distructive effect. It isn't your fault. It doesn't mean the issues are necessarily real, and there are people who can help. So please please talk to someone.
Sending massive hugs. x