I think Lux asks some good questions and poses some things to think about.
To be honest, though, when I read the OP, my immediate answer was that it's not an INFJ thing at all - that it has nothing to do with being INFJ or any type (I've seen extroverts of all types post similar things from time to time on this board - so it has nothing to do with the number of contacts you have or the amount you share). That it's a human condition, that everyone experiences this from time to time. Maybe in varying degrees, but I am quite certain this is a side effect of being a sentient being. After all, we are and always have been in our own mind, and are unique individuals, the only one precisely like us with the same set of experiences in the world. And our awareness? All of our thoughts and feelings and all of that? Yes, we can share of ourselves, and become closer to those we share to, but we'll never find someone who will KNOW who we are, precisely, as they aren't us and aren't in our mind/body. They'll never *really* know what it's like to be us - to look out at the world with our eyes. No one will. The reverse of this is that we can't possibly know what it's like, really, to be in another persons' mind with other thoughts/perceptions spinning around. But I guess I've gained a sense of peace with this over the years.... because I take heart in the fact that everyone else is in the same boat as I. So that relieves the loneliness a bit, and it also provides the bridge/opportunity to feel more of an affinity and closeness to others. Ironically.
But yes, sometimes I'm horribly lonely and feel utterly alone in this world. I see those bubbles/moments of feeling as 'normal' though - normal to everyone on this planet.
And, your need for love might not ever be fulfilled in the way you really desire by any one person outside yourself for all time, at the deepest part of your core... if this is a fact of life - a reality - do you think you would be able to reach a point of peace/comfort with this? Do you think you would be able to accept it? I think a part of the intense loneliness is a dissonance, not wanting to accept that this might be the case, not wanting this to be how life might actually be (at least sometimes)... but if you would be able to accept it, the dissonance might slowly flow away or cease to have power or prominence in your mind.....