If you breath in energy that you cannot feel, continue with the meditation until you can feel it.
Basically if your nervous system is used to lots of energy, it's likely that you'll have a harder time feeling energy at low repetition of breaths, and as the number of breaths increases so too does your sensitivity increase.
If you are new though it may be difficult to exceed a certain number of breaths and this is a sign that you are breathing in energy and you have exceeded or are nearing the limit of what you can safely absorb for that session.
Alternate nostril breathing is a great way to increase the number of breaths/amount of energy you can take in during one session as this acts to balance the ida and pingala which re distributes the absorbed prana through the channels and thence enables your nervous system to handle it better.
HAIL SATAN!