Observed hundreds of clear orbs in the sky appearing to be looking at me.

I am 38 years old now and have been troubled for years over what I experienced at the age of 19.  My boyfriend and I parked at a rest area off at I-75 in Lansing, Michigan.  We stopped there to make out, talk, etc.  
After being there for about 5 minutes, we suddenly noticed hundreds of iridescent free flying circular clear orbs that came closer and closer to our car.  They seemed to be observing us.  I couldn't believe what I was seeing.  They came as close as only 10 to 20 feet away from the car.  At that time, I became very afraid and we left the rest area.  As we drove off, we could see them flying back up into the sky as we got back on I-75.  
This has been driving me crazy for years now, as I am a very logical and scientific person.  I haven't told very many people of this event because I know most people won't believe me, but still after all these years I think about it at least once a week.  I am glad to finally share my extremely bizarre event that ha! ppened to me.  
To this day, I can't find anything on the internet that can relate to my happenings.  Over the years, I have wondered if this could have been a paranormal event rather than an alien experience.  If anyone out there had this happen, please let me know.  I feel so alone with this and will take it to my grave wondering.  I just want to know what this was.
Witness indicates that the date of the incident is approximate.  PD