How do I find out what weapon I'm holding in battlefield bad company 2 campaign?

You need to go to the supply drops and pick your weapon, which tells you the name of all the weapons you have collected during the campaign. Also, to make it easier, as you play, try to remember what each weapon looks like, and the way it fires, for example, the AN-94 shoots with a 2 round burst. Try to remember things like that.