That's why observation is important. If they are unwilling to talk, their actions will speak for them. If you notice he is spending less on things he will normally splurge & spoils you less (or let you eat spagetti but he makan roti kosong), they are probably having money troubles. Then you pandai-pandai belanja him sometimes, spoils him a bit. It's do wonders to help cheer them up and supporting them when they are down. Not only girls need to be spoils, guys love it as much too.

But I personally think if you are in a relationship, you should at least let your other half know your problems. Sharing is essential or a lot of trouble may cook up due to miscommunication and misinterpretation.