What does being Hypnotized feel like?

Well the first thing to keep in mind is that you are aware of what's going on at all times and in full control.

It feels very much like when you are day dreaming or that feeling just before you fall off to sleep or just wake up.

I don't think I can be Hypnotized.

The truth is that everyone can be Hypnotized if they want to be ... in fact the higher the IQ the easier and deeper the trance. 

Generally only people with an IQ below 70 or with health issues like Schizophrenia are unable to be Hypnotized because of their inability to focus or concentrate.

Will the effects be immediate?

Each person and issue is different, some effects will be immediate but will also be a number of changes developing over a period of time.