recurring nightmares since i was in the third grade

I am now 18 years old but I have a lot to say about my nightmares. I see many people are having trouble with their nightmares but to me its something I don't freak out about anymore. There was a time where I would not want to go to sleep, I would wake up crying, I had to go to counseling because of my nightmares and I went through depression because of my nightmares. I still remember one clearly.

When I was in the third grade I remember having this nightmare. My family which was only my dad mom older brother younger brother and I were going to this house. Looking from the outside it looked like an old abandoned church. It looked haunted and there were skulls on the door. IIn the dream I was afraid, but my family seemed super normal about it as if nothing was wrong. It was freaky, I knocked on the door at the doorknob which was black just like the rest of the house there popped out an eye. And the doors opened by themselves. I can continue with all the exploring around and stuff but I'll skip that. There was a point where my family members began to die. I found my little brother hanging on the ceiling along with many other skeletons. I couldn't find my mom and dad, my older brother disappeared in the dream i I only saw him in the beginning of it. I had a feeling in the dream that my dad was dead. I finally find my mother, she was sitting on the toilet. But when I saw her she was happy and she gave that beautiful smile she always gives me she said hi, she wasn't worried of what was going on and I wasn't either anymore. Then at an instance a hand came out of my moms mouth tearing her down and then a hand came from under the toilet and pulled her into it and all I remember is there was blood everywhere.

I was never the same kid again after that. I remember sitting in the Car crying my eyes out not wanting to go to summer school and I told my mom what I dreamed , after that I couldn't sleep. I kept having nightmares every single night. And from that point until Noe I have nightmares just like that. Now that I am older they are different. I dream about killing, sometimes people who threaten me sometimes people who don't do anything at all. The past few times it was people I know, and I actually like these people and these were very vivid dreams.

I don't use weapons I use my first in the dreams and I am always the one dominating. I have been in a few fights and yes I am a very violent person. And through tout the day I stay mentally ready to defend myself in case of anything. I have a job, I work well with people I am very professional, but I also have my own state of mind. And I learned to accept these nightmares that I don't even consider nightmares anymore. And I can sleep through them without even waking up breathless. I just go on with my day as normal.

But one thing that's bothering me,I had a dream that I killed one of my coworkers which I really like he's a good guy, but ever since that dream I have come to realize that he's really annoying, and I have been thinking about confronting him lately about it but I decide not to. He jokes around sometimes and can be disrespectful but never have I realized how much it bothers me and I am now taking it personally. I am very good in controlling my emotions though and if I did deal with it it would be in a professional manner. Give me your opinions, and if you know about dreams if you think I should be concerned leg me know too. I know there are mental illnesses out there that mess with your dreams

You are in the right place for dealing with nightmares. You have also discovered unfortunately the function of nightmares. If you decide to ignore them, they will persist until you are forced to deal with whatever is causing them. This could be dealing with them positively, or a violent venting of whatever has been latent this whole time.
Becoming lucid and exploring the content of your nightmares can be a life saver. That is how I learned to lucid dream naturally as a kid.
Lucid dreaming is not the only way to explore and solve this issue. The main thing is to engage these emotions, and exercise some self reflection. This can be done through therapy as well. The psychological functions of supression and repression are not easy to work through. Many times, it is a smart idea to have some educated help to guide the process.
In dreams, the natural healing function of the psyche helps guide the lucid dreamer through the labrynth. Any way you decide to go, uncovering the unconscious repressions is key. I wish you good luck! :)

One thing to keep in mind is that normal people have crazy dreams. You mention mental illness as a possibility, but what you have to keep in mind is that for mental illness one needs to be crazy in waking life not just in dreams, so if your waking life actions and thoughts are within the normal range but only your dreams are crazy, that's not as worrisome as if waking life concerns make you wonder whether you are crazy.

Another thing to keep in mind is that dreams tend to exaggerate. Killing in dreams does not necessarily mean that one has homicidal tendencies, not unless one also has them in waking life. A dream of killing an annoying coworker may just be about venting your annoyance with him. I once posted to Facebook about a former coworker of mine that if he is found dead the next day, I shall need an alibi. But I did not really mean it, I was just really annoyed. In dreams though those kinds of metaphors are shown more realistically, so even though we don't really mean it, we may dream of it very realistically. As long as we do not really mean it upon waking, there is nothing wrong with that.

Yes, I do think that you may want to consider lucid dreaming because it is a great way of dealing with nightmares, alternatively dream interpretation may help - if you get to understand your dreams better perhaps you will feel less concerned about them. If you have concerns about your waking life psyche, then therapy may be advisable, but if all that is crazy are dreams, as I said crazy dreams do happen to normal people - though therapy can also at times help normal people deal with our issues better, but it may not be needed.