Sorry but your funds was already stolen and you can't retrieve it anymore. Can you remember the software and apps that you have downloaded to your PC?
Let's say that you have been aware of protecting your security all of the time but you probably missed some random apps that you have downloaded and didn't noticed it as you use them.
That's true and that's one of the risks of keeping all your funds in a single wallet. I think you have downloaded or have clicked phishing sites that might hacked your wallet. It's a lesson for you to learn. You should secure your wallets and be mindful of every click and download that you will be doing. It's just sad that you have lost the funds that you have worked for.
It's very sad because OP needs it for the operation of his mom and this kind of incident did happened to him, very frustrating.
...
Next time it will be best if you use a much more secured wallet like blockchain or your local exchange if you have some so you can easily reach the customer service in case there is a problem in your wallet like this one.
Blockchain or a local exchange? Those are bad ideas unless you are incompetent about securing your own computer. Then you don't own bitcoin, you have an IOU.
Electrum is secure if your computer is secure. People saying that "they" have lots of security issues are misinformed.
People never learn about keeping their funds with an exchange, local or international. I understand that they like it keeping there so that they can easily sell it if it's needed but they don't realize that once the exchange gets hacked, they can't retrieve it anymore unless the exchange is generous to refund the lost funds of affected users.