Keep in mind that as an INTJ, you're likely to invest only in those people that are really special to you - a small circle of friends. That means that those friendships have a lot more weight to them. Other people who are more focused on socialising than your type, however, will have likely bigger social circles with a lot of different levels of friendship in them because they prefer to spend the bulk of their energy in that field - it's their specialty whereas yours typically lies elsewhere.
In other words, you're responding to this because you see this through your own view on the world - you wouldn't have the energy and time to invest in all those other people, and so you would run out of resources that each person in your circle deserved, hence you fear that you may become the victim of that perceived lack of resources, in turn. This is aided by what I assume is an inability to actually gauge where you stand in a friendship with someone else, since you likely don't (yet?) invest in the multitude of friendship layers that others readily use.
The first is easily remedied by reminding yourself that others don't work like you and unless you actually notice a drop in the friendship, you have nothing to worry about as they manage their resources differently than you - and likely more efficiently.
There is also no need to compete when it comes to relationships - leave that for the professional field as it can seriously backfire in the relationship department, and actually destroy the relationship due to the fact that you're trying to control them and their affection. People aren't just resources and goals to be obtained. It takes two to tango in a relationship - it's more like a dance and while you may have a preference for the kind of bond you like, there is nothing inherently inferior or superior to what type of bond you have with a person. There's just making sure you're on the same page, have the same expectations and actually get out of it what both of you want. If not, go your separate ways or find a way to adjust your expectations
As for the gauging thing...just ask. It'll take a bit of courage, for sure, but if you have the kind of friendships where vulnerability has its place (and those tend to be the most intimate and close relationships), they'll be ok with you asking and won't mock you for it. If not, you've got to wonder what you're really competing for and what the point of the relationship is. This tactic has the wonderful benefit of a) helping you develop parameters for gauging where you stand with people - and thus addressing that insecurity with much needed information, b) strengthening your bond by sharing your fears with the other person and c) being the direct opposite of being competitive, thus forcing you to actually learn to shift between professional competition skills and relationship-building skills.
As for how to actually do this: 'Hey, I have a request. This may seem a bit silly but, I find myself sometimes wondering just how close we are, at times, and it can mess with my head. Could you tell me (insert thing you're wondering about - closeness, how they view the relationship, what they get out of it, etc)?'
Be sincere, open and if you can't stand feeling that vulnerable, add a little lighthearted joke or chuckle to put yourself and them at ease.
/two cents.
