Thoughts of death and impending doom?

I have always had the same kind of thoughts, images daydreams and horrible thoughts flash through my mind to the point I have to physically stop myself. These thoughts run through my head and I experience, anger, panic and even feel sick. I am 33 this year and have started getting used to them. I thought that I was quite evil having these thoughts, why would a normal person have horrid thoughts about people I love, the answer is just that, you have these thoughts because you love and care for them, apart from these thoughts I also have planned out in my head how I would react and take revenge etc. I think as disturbing as these thoughts are they are unfortunately natural for people with over active imaginations. I have not had any therapy just as soon as I start thinking about these things I breathe in deep, shake my head and get up and walk away from whatever I am doing.