I've been meditating for 10 months. I am observing my nostrils- breathe in and out. When I meditate, after the 5th minute my breath becomes really short and I feel like my chest area has become very heavy and I continue observing that, but the body does not take deeper breaths. My last meditation was even more strange- the breathing in continued for about 2 and a half seconds, holding in for 1 sec., breathing out for 2 and a half seconds and not breathing for another second. The intake of breath is really small- I barely feel the air in the nostrils- and I know this is a normal thing in meditation, but are such short breaths normal?