Credit glitch?

Hi,

I've just played Mass Effect 3 Multiplayer, I can't host games or play with my friends right now so I was a pick-up player in a group that had already won two waves (if I remember properly). I had a few issues during the games after one or two waves. For instance, my gun wouldn't work properly, I had too much ammo, but after I shot it would write "-12".

Since I've had bugs like these before (invisible ennemies, invisible allies, invicible ennemies, ennemies spawning inside the walls), I didn't think much of it and carry on with the game. We won a bit too quickly (I'm still a newbie) and the host left the lobby very very quickly after the game.

After that, I spent my credits on some packs as usual, but I realised I had more credits than usual and speding it was working, so I stopped and quit the game, launching it again to check the ammount of credits I had. The ammount isn't changing unless I get some packs so I guess it's some kind of glitch or something. I had a chat with EA Assistance and they couldn't help. I talked to a friend who said I might have played with a cheater, and looking on the web got me quite scared. I have only started to get truly into multiplayer and I don't know about all the glitches or cheating that can happen.

What should I do? Is there a way to get rid of the extra credits? It's not even fun to have so much and kind of ruin the game for me. Should I just stop buying packs until it's all normal again? If I play the game again, will it return to normal or just keep adding new credits?

Is my account going to be banned because I didn't know something was wrong?

EDIT:

I found this post and sent an email to [edit: email address removed] to inform them. I hope it'll be fine.