If you understand a little about bitcoin, you surely know that all your transactions are public in the blockchain. So, if somebody knows that you own an address X, that person will know all of your previous and subsequent transactions involving your address X.
So how to remain anonymous in a Bitcoin transaction?
Well, you can mix your coins with others coins, this method is known as CoinJoin. There are several implementations of CoinJoin available and one of them is Whirlpool from Samourai Wallet. I recommend you do your own research since you're your own bank.
Look a video demo using Whirlpool on mobile:
From today until friday (October 6-9) you can have 15% off Whirlpool mixing fees! Just use the discount code: HURTMYFEELS
Just sharing.