You seek professional help, like I am doing. Counselling, therapy... whatever you want to call it. My head is fucked up like that too. I have vague ideas as to why, but I'm not in control of my wildly shifting states of mind regardless of how much I might understand the path to my current mental health.
If you are thinking about suicide, even if you're not serious about going through with it, but are being so overwhelmed by emotions that you don't know how else to react; speak to a doctor. Trust me, you'll be doing your future self a favour. She will thank you later.