how to reset my weapons and levels in bf3?

OP it is not possible to reset your soldier back to level 1 like the COD Prestige function.  Your only option depending on your platform is to make a new account and link it to your existing Origin account.  On PS3 this is free and if you link it to your Origin account and you're Premium your new soldier will also be Premium.  On Xbox this requires a second Xbox Live Gold Subscription and a new BF3 online pass for $9.99.  I don't know how this works for PC, but since your online pass is associated with your Origin account on PC you will probably have to purchase another online pass at the minimum for PC. 

There is a lot more to do in the game to extend your play - you can go for weapons mastery tags, there are a bunch of assignments from the expansion packs to do - and many more assignments if you become a premium member.  If you've only been using a couple of classes you can expand your game by using classes that you normally don't which really changes the way your game experience is.  I've actually got four soldiers, a Colonel 28 and a PVT 2 on PS3 and a Colonel 02 on Xbox, and a level 21 on PC and I play each one differently which had greatly extended my enjoyment of the game.