From your second post, it is 100% clear.. The condition what you are sufferring through has it's name in medical term "Obsessive Compulsive Disorder (OCD) " or in general - "Scary thoughts". It is a part of anxiety / depression / mood disorders. Lots of people suffer it. YOU ARE NOT ALONE. Check this forum:  http://bbs.stresscenter.com/eve/forums/a/frm/f/372105472

People with such conditions.. have feelings of "what if i stab myself" - when they hold a knife.. or "What if i jump of here and kill myself" - when they are in high buildings.. Some people..even 'scared' of .. they would just kill their infant baby while taking him bath in bath tub.. I mean there is no limit of what might pop up in mind..

SO, first thing... SEARCH ONLINE.. "Scary thoughts + Anxiety + depression", and educate yourself.. It is a great relief if you find some word to attach to what you are suffering from. People get more suffered when they dont even know they are suffering from depression/ or OCD. You have the same problem.

Next, you should seek medical help. Therapy also works. But your case seems clinical. You need to talk with doctor. Tell him you have "Obsessive Compulsive Disorder OCD".. DONT WORRY - Once you overcome  this disease, you will feel different world. Everything will be normal..

NEVER EVER STAY AWAKE AT NIGHT.. SLEEP IN TIME and WAKE UP EARLY .. go for walk.. and IMMEDIATELY SEEK MEDICAL HELP.. There is nothing wrong.. about this. 

1. Take good quality vitamin B complex.../ multivitamins..

2. Take fish oil capsuls

3. Drink Enough water .. even when you are not thirsty.

3. Never watch sad stuffs..  watch comedy.. and funny stuffs.

5. Sleep in time. .wake up in time.

6. You can get test - what mineral deficiency is causing the problem in your body.. You might need to take 'folic acid supplements, or magnesiums or chromiums (these are in deficiency in most of depressed people..).  Your doctor can tell after undergoing some clinical tests.. 

7. NO alcohol/smoking.. AT ALL.

8. Talk /discuss with friends. JUST BY DISCUSSING WITH THIS FORUM helped you a lot.. i guess..

9. Active lifestyle.. play games.. go out.. hang out.. life is beautiful..

Try some links

http://bbs.stresscenter.com/eve/forums/a/tpc/f/541105472/m/1711050945 

(Midwest center have audio talk therapy materials.. you can find them in torrents.. search "attacking anxiety and dipression" torrent.. and download..listen.. people discussing their scary thoughts.. and how they fought back and overcame it..