its normal for you to feel this way, in fact i guess every women has this fear of their husband "eating outside".
the thing is not to let this fear creep over yourself and causing you to suspect at every single detail that your husb does. It does nothing but harm to your relationship as well as affecting your daily routines. Its not healthy for you in the long run. And you might lose mutual trust too.
the credit card bill for 2/3 pax is not really an important detail. It might just be lunching with a colleague.
Perhaps next time you wait for him to initiate. Rather than you taking the first move?