How can I know if someone hacked my IP address?

[Jesus]

The thing is that there is a group of people that are trolling ullying me because some girl didnt like me.

In their facebook accounts they mention the theme I touch for example, diabetes, I made a question on diabetes and they talk about diabetes. Is there any other way besides a keylogger to spy on someones computer?

I know I man that says that he can see the persons IP address in youtube,,,but he is not my friend.

It seems that a ''friend'' of mine was convinced by them, maybe I am wrong, and he was convinced that I am the one who is trolling them. This ''friend'' had an Anonymous friend and another user accounts with rare names without information. Seems like someone is trying to disturb me.

How can I detect if someone is spying on my computer?

How can I stop this?