Hello Horatia, welcome to the BB forums.
I'm not qualified to say, however as I've had similar thoughts, I wonder whether you have had a diagnosis, I only say this because this could be having 'intrusive thoughts', which are thoughts that seem to become stuck in your mind, cause distress and certainly make you upset and can occur frequently.
Anxiety can cause someone to get OCD which these thoughts do happen, so we'd like to know whether this suits how you are feeling.
I have OCD and had these thoughts along with many other people, so if you can place 'intrusive thoughts' in your search browser, a large folder will develop.
Hope to hear back from you.