Hiya Amy -
it is always good to talk about such bothersome and troubling thoughts and images. I find it interesting that you experience them not only in depression, but also in boredom. The latter is not that usual, IMHO. 'Boredom' suggests a state of mind that is relatively anxiety-free, perhaps a bit apathic, without too much initiative, and lacking enjoyment. That's not a situation in which our mind likes to confront us with unwanted, intrusive stuff.
I do not know what you mean when you write: 'feel like a terrible person'. Does that imply: uninteresting, repulsive to self, repulsive to others, redundant? If that is so, then clinical depression might plague you. That is a disorder that can in principle be treated. Do you think it is related to OCD in your particular case? The suicidal thoughts also point to such a condition, as does your temptation to act upon them. There are people with OCD who also suffer from suicidal thoughts, but, contrary to you, are terribly afraid that they will realise them - whereas you write like you feel seduced by them.
That you don't know how to cope with all this is perfectly human. No one can. That they interfere with your life in a grave manner: likewise.
So: it looks like you suffer from a combination between OCD (i.e. intrusive thoughts and images - is that without compulsive behaviours?) and clinical depression (or MDD, major depressive disorder). Do you have any form of therapy? Do you use pharmacological stuff to alleviate your problems? If not, you should really seek clinical help; the problems you put before us are very serious, and can normally hardly be acted on by the person herself.
That is what I can write in the form of a reply. Sorry if I come over as very inquisitive... it's that you keep some things to yourself, and you are of course completely entitled to do so.
I'd be grateful for some more information. If you want to provide that, please PM me (private messaging; to be found behind the 'profile' button). It's all up to you, and out of Holland I wish you truly all the best with trying to overcome the obstacles that you describe.
Cheers, Cuthbert.