I think this is just normal hormonal changes that occur during pregnancy. It would make sense that this pregnancy would be more emotional being that you've previously had a miscarriage. I wouldn't worry about it too much. They do have anti depressants that are ok to take while pregnant. If you feel like this depression is becoming more of a serious problem, you should ask your doctor to prescribe some. It is better to get this taken care of now rather than assuming things will be back to normal after giving birth. Postpartum brings in a whole new batch of hormonal changes and you don't want to struggle with postpartum depression if you don't have to. You should be able to enjoy this and your new baby when it arrives.
Like I said, I think it's just normal hormonal changes that you're adjusting to. But you know yourself better than anyone else and if you feel like it's seriously depression, get some help. It doesn't make you weak or a bad mom. It makes you a better person for recognizing a problem and taking steps to solve it.
Good luck