Peculiar Experience of Shamatha / Vipassana I'm currently attempting to do shamatha and vipassana meditations in alternation, even though I'm unsure this is the best way to proceed. I noticed that generally, as a person, I am somewhat repressed in the sense that few thoughts, images or sensations seem to emerge. 

There are a few other peculiarities I experience, and I'm unsure if people could help me with that. I remember vaguely as a child having odd sensations / visions which arose without reason, in mandala form usually. And since a while now, I seem to be gaining insight randomly, sporadically. I've been happy for years, not in a strong pleasant sensation but in experiencing equanimity generally or lack of attachments. 

Yet, I'm feeling stuck in my practice because I don't seem to realize where I'm at. I don't know whether I have good or bad concentration, or whatever else. I seem to be unaware of my own mental states. Since I feel repressed and few images or feelings arise, I think perhaps vipassana would help, but ultimately, I dunno.

Any kind of help on what I'm experiencing would aid me greatly, and I'd be willing to supply more details if necessary.
Your question gives the impression that you have not developed meditation within a certain teaching/practise tradition for a prolonged period but have been learning theory from different random sources. If that is true, your question thus gives the impression the various theories of meditation have confused you. 

In the West, there is a popular form of 'meditation' from Burma that is erroneously called 'vipassana', where practitioners are preoccupied with noting thoughts, images or sensations. This is so because practitioners have many distractions so this method accommodates &amp; attracts those kinds of practitioners.  

In formal Buddhist theory (such as in the old scriptures) having few thoughts, images or sensations is a good thing. In formal Buddhist theory, samatha &amp; vipassana are developed in tandem (concurrently), with samatha predominating in the beginning &amp; vipassana developing naturally as samatha deepens. 

In formal Buddhist theory, 'vipassana' does not mean noting thoughts, images or sensations. 'Vipassana' means 'seeing clearing' the impermanence &amp; selflessness of phenomena. 

For example, on a very basic level, the mind can develop samatha by continuously observing the breathing in a balanced equanimous way. As the mind is continuously observing breathing, it will naturally notice the breathing is impermanent; in that the breathing comes &amp; goes; that it becomes short &amp; long; that the various breaths have different textures &amp; qualities, such as being smooth, rough, agitating, soothing, etc; ultimately to the point of seeing clearly it is the body that breathes (rather than "I" or the "self" that breathes). Seeing clearly the impermanence &amp; selflessness of the various breathing ins &amp; breathing outs is real vipassana. 

Then as samatha develops &amp; deepens, certain feelings of rapture &amp; joy will predominate in the mind. When these feelings predominate, they will also be objects of vipassana, in that the rapture &amp; joy will be seen as dependently arising, impermanent &amp; selfless. 

Then as samatha deepens, more profound vipassana will occur in different ways. 

Therefore, in my opinion, you should consider developing samatha more because this leads to calmness &amp; non-confusion. You should forget about thoughts &amp; images because these are actually hindrances to meditation.

The 'sensations' that are ideally observed are the subtle sensations within the breathing; the sensations of the breathing being smooth, rough, etc. Then later, as samatha is profoundly developed, the mind observes the sensations of rapture &amp; joy that arise from the calming of the breathing. 

After this, the mind will be very clear &amp; can discern the 'dependent origination' of thoughts, consciousness, other mentality &amp; sense objects. 

The classic original Buddhist path is based on developing samatha. Further, based in what you described in your question, the impression is your mind is predisposed or inclined to develop samatha, since it has equanimity &amp; few attachments. 


  [And] for him these two qualities occur in tandem: tranquillity (samatha) &amp; insight (vipassana).
  
  Maha-salayatanika Sutta