well it's kinda easy to say 'he doesnt care so I dont care' but just as you will be pretending not to care (or forcing yourself not to) so might he. the things we say with voice and look arent so often the things we feel deep down.
I never believe anyone who says they dont care and I've heard a few. If they really didnt care they wouldnt need to say it.
human beings are masters at hiding things - and especially from ourselves.