An introvert, then.
Well, I, too, am inclined to that. I have many fewer friends than, say, my wife has, who is much more naturally extroverted and sociable. However, I note that while her friendships get spread out broadly, mine appear (at least to me, and I think, and with reason) to be much deeper, involving much more loyalty and a deeper level of connection, than those she routinely has. For instance, all my friendships are of the "pick-up-where-yoy-left-off" kind, and all of them go from trivialities and "how've you been" kind of conversation to much deeper, more honest stuff in very short order, relative to hers. Hers seem to require a lot more surface conversation to get going, and she seems much less assured of the goodwill of all her friends than I am, even though her friends are very nice. And honestly, I feel I would not trade all of her friendships for even one of mine.
Could it be that the shortage is in those sorts of connections, so that casting about among your acquaintances fails to reveal the kind of friendship you require at this particualr moment or stage of life...through no fault of your own, perhaps?
Again, I'm just throwing guesses for you to entertain, not making a judgment.