Some services, especially exchanges, may move out the money from your account according to their needs, but also keep your account credited.
But since you are not credited, the chance of theft/hack is pretty big. Did you log in to your wallet from an e-mail (phishing)?
However, you should start with asking for help at the support of the service that handles your wallet, telling that your account is not credited.
If your money got indeed stolen then you have to disinfect your computer, change passwords or even make a new account
That sounds potentially very disappointing. I'm using 'bitcoin wallet'
You need to be more precise than that. All bitcoin wallets are ... well.. bitcoin wallets. It's a web site? What's the web site's address? Or you can make a screenshot and draw over sensitive data in Paint.