But with your basic security of no file or printer shares and a firewall it should be fine. But your post is without details so not much can be said if it is or is not ok.
Ok well I've been having issues with an online video game, so I tried putting my router in DMZ, and it worked, but the time that I had it enabled for like 10-20 minutes, I didn't have my firewall/antivirus on either. So I'm kinda paranoid that someone could've hacked into my computer and/or gotten any passwords for my online things. Should I be worried?