I was sitting on the front porch with my wife, it was near dusk and we had been watching for deer. We heard what sounded like a helicopter flying below the ridge line of the mountain behind us to from the south end to the north end. This concerned me because I could not see the helicopter but I could hear it and it was moving pretty quick and low. My wife went inside, I then walked out into the front yard and heard a roaring noise coming towards me from the west. I did not hear the sound until it was almost directly over me. It passed directly over my head at a speed I would guess to be around 3-5 mph. I was shocked by what I was seeing but I kept my head and never took my eyes off of it until it was gone, I will admit I was a little scared. The object had a green light in the front and blue and white lights in the rear. I would estimate it to have been about 100 feet long. The front was very narrow and grew in width with a wingspan I would guess was around 75 foot. I would not really call them wings, it is hard to describe but I could draw them. The object was gone as quick as it came and I lost sight as it continued to travel from west to east. The trees were bare and it just seemed to follow the treetops down the side of the mountain until I lost sight of it. After it was gone I was afraid I had seen something I shouldn't have. having had worked for a defense contractor I had a lot of exposure to military aircraft and I surely could not think of any planes that could fly that low and slow being as big as it was. I was afraid to say anything, I knew I had just seen something that changed my life, the way I thought about things and I even stopped going to church. I still have not told anyone what I saw including my wife and I probably never will. I think about this event almost everyday. I see military aircraft in my area a couple times a week but nothing like this object. At the time I held a government clearance and was afraid to say anything. I no longer hold any clearance and felt like I needed to get this off my chest.