Sad partner

Samantha
My fiancé and I have been trying to have a baby for 10 months now without any luck. 
I'm on 100mg of clomid and we have sex every other day sometimes everyday. 
He's beginning to say things like "we're never going to have another one" or "God doesn't want us to have more" 
I have a 7 year old daughter who isn't his. And we had twins two years ago but one passed away shortly after birth. So our survivor is almost 2 right now. 
What can I say to help him be positive again? Him being negative really makes me feel negative!