Yes, I have certainly felt this way too. You have a lot on your plate and chemo is wearing you down and perhaps even causing hormonal imbalance. Don't forget to let your doctor know about these feelings.. even if you don't want to take medicine for depression they might have resources you can look to for some assistance.
It's funny-- you'd think that being halfway done would feel better, but the effects of chemo are cumulative... the ride downhill seems just a difficult as the beginning. Hang in there :)