It is easy to get depressed and suicidal without the proper nutrients in your body. Also, genetics plays a part too.
From the sound of your message, it sounds to me like you should get a very high dose of fish oil into your system 3 x per day (for brain health, depressive symptoms), Vitamin B12 (for obsessive thoughts), Vitamin D3 10,000 iu's daily (for Depression and anxiety) and magnesium (for depression/anxiety).
Don't worry about the paras - for now. Get your emotional health sorted first. Do not take your life as your call is to sort this out, not jump ship. We all have worms. We are animals after all.