A child hood experiece seems more real like an alien encounter then the "dream" I thought it was

For 65 years or more I've thought of this experience as a bad, bad nightmare.  The more I think of it the more it seems it was not a dream.  It was the most frighting thing in my life. 
I was about 4/5 years old when the first occurrance happened.  Two/three  creatures appeared in my bedroom at night.  They just came thru the wall and where there.  I was scared to the point of hysteria. 
The next thing I remember is we where going down the street away from my house towards the nearest corner.  There was their "car," as I thought it was.  I noticed it was shiny like polished alumimun (not black like all the other cars I'd ever seen) and it appeared to me to be upside down!  The flat part was on top and the curved part on the bottom, like a half sphere upside down.
They wanted me to get in and I guess I did although I can't recall.  After that I was afraid to go to my room to sleep because I was fearful they would come back to take me.  I think they returned maybe 4 times.  I was always near frighted to death each time.  As best I can recall this was over a period of about 1 or 2 years.  Then they stopped coming.In my pre and teen years I was very prone to nose bleeds. 
This in its self was not remarkable except for one occurrence. I was having a particularly heavy nose bleed. and was leaning againist a building letting it just run freely.  Some thing came out of my nose and fell to the ground.  I didn,' pick it up because it was all bloody, but it was maybe a half to one inch long and shaped like a bullet.  I've always wondered about that. 
I am now 72 years old and have never spoke of this to anyone.  Am I nuts or imagining some thing??    
My name is ((name deleted))
Witness indicates that the date of the event is approximate.  PD