It can mean that you think something is true, for example "I can't help feeling that I am going to be fired soon." It can also mean that you are feeling a certain way or emotion, and you can't change or stop it. Example: "I can't help feeling angry with him."

We usually use this to mean that you have a very strong impression about something. For example, if you say: 'I can't help feeling that you are laughing at me.' 'I can't help feeling that he is wasting his time.' this means that you think that this is the case. You can't be sure, but you very much suspect it.

It means "I can't avoid thinking that..." for example have a look at below The scars of your love, remind me of us. They keep me thinking that we almost had it all The scars of your love, they leave me breathless I can't help feeling... It means "I can't avoid thinking that..." Here it is referring to the next line. She keeps thinking that they could have had it all. It means it seems obvious to her that they could have "had it all", been happy and together for life.

I think it means someone who can't control his emotion to something.