Paranoia

I have a problem, and I come forward to you completely embracing it. I know to many it will sound ridiculous, to many it will seem perfectly logical, and to some it will suggest I need some sort of mental help, but stick with me. I have an amazing ability to repress my paranoia when others are around. You wouldn't know just by looking at me I am paranoid.
I am paranoid of intruders. Intruders of any kind, be it kidnappers, burglars, murderers, and any other category I'm forgetting. I have this unexplainable fear of them. I have thought long and hard of every scenario that could possible happen if someone broke into my house while I was home. I have an escape and/or attack plan for every room. Evaluated various objects in each room and determined what I can and can't use as weapons in self-defense. The kitchen/dining room is always the preferred place to encounter an intruder, because it has two doors I can easily access and all the kitchen utensils to use as weapons! In my room I sleep with a fork on my headboard.... I know how weird that sounds, but think about it. It does just as much damage when jabbed at a human being as a knife does, but looks ten times less threatening. In the event an intruder passes me by in my room, if I'm lucky enough, my bat bag is also within reach so theoretically I can get my bat out too!
 I especially put these plans into thought when I am home alone, like I was today. I came home to the front door unlocked, which I automatically assume means somebody is home, but found no family member present. This sent me into automatic lock down mode, as a number of things could have happened. I mean, who knows how long the door was unlocked! Anyone could have walked right in before me and could be waiting inside for me. What if someone came in and, heaven forbid, TOOK my sister or something, and was waiting for me next?! The tv was on and my sisters' backpacks were here, so I knew they had been home. I double checked every room, and concluded no one was here, so I went to the kitchen to get a drink and settle in, though still puzzled by the situation. But I heard something from the back of the house, and without hesitation I pulled out the CHEF 2000 6.8 inch knife from the knife drawer and kept it at my right hand side, ready for whatever monster was back there breathing our houses air and prepping to pounce on me. Though, I continue to go about my business, mind you, I just happen to be on high alert while doing it, with a knife in my right hand. I decide to stay in the main areas of the house and not go back to the bedrooms or computer room, cause it's a lot easier to be trapped back there. I lock all the doors, and sit down to my laptop. I place the knife facing behind me prepped for an attack from behind. And like that I sat until my mother came home to relieve me of my concern.
Not that having my mom in the house would stop a murderer in the moment, trust me, I've mulled over that one for days too. But it puts one at ease to have another human around.
This is what I live with. And the scary thing is I don't mind at all. It makes me feel safe, even though I've never been in a situation that even remotely come close to the intruders I make up in my head, I am prepared! You think I'm crazy? Is this normal? Do I need professional help?