Social media and relationships

How do you gals feel about Facebook, Instagram, etc. involving your relationships? My 'boyfriend' doesn't ever interact with me on anything, won't post about us or put up any pictures, won't make us "online official", blah blah. I know it shouldn't bother me, but it does for some reason. 
We're also long distance (known each other almost four years, been together for one) and I don't think he's really told anyone about us. I don't want to assume the worst, that he's got someone else where he lives, but I also don't want to be a fool...