What is wrong with me?

For about a year now I have been having obsessions about death and suicide. For example, I recently found out that someone I went to school with hung himself, I went go to the zoo and had unwanted thoughts about jumping in with a crocodile, thoughts about hanging myself, harming my partner, jumping off a cliff etc. After each thought whichever one it is I then find myself in a situation where I would yze the thought in detail and think "what if i did that? How would it feel?" etc and then I get all emotional about it and my jaw starts shaking and I am forever worried that I could do these things and that I am going to end up losing my mind and going crazy. I don't want to act on these thoughts. I am scared because I don't have much control over them and they are interfering with my life. I have also noticed a change in my mood occasionally. I snap at people more often than I used to and it bothers me immensely. What is wrpmg with me?