Yes, yes, yes you can attribute it to hormones. After I had ppd, my next pregnancy I was depressed from like 5 weeks on, to varying degrees. It actually didn't get worse after the baby was born but everyone is different.
You CAN treat it! Bring it up at your next prenatal appt. You can try a completely natural route first if you want--supplements, diet, exercise, light therapy, etc. Or if that is way too hard to carry out, just do as much of that as you can and start some antidepressants. I think Zoloft is the most common while pg? It is not without risks but if you are miserable and pretty dysfunctional.....it may be the best answer.
Anyway, mostly wanted you to know that you don't need to wait until post partum to get treatment.