Short breath during meditation

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?

May I ask, after these ten months...what can you tell of/about your motive to practice and expectations thru meditation.

I'll have to explain more thoroughly. The short breath and the heavy chest feeling I get in meditation are uncomfortable. This breaks my concentration and my mind starts to wander, count seconds etc. And I have heard that people feel bliss in meditation. My question is whether that is normal to occur in meditation? And if not, what am I doing wrong?
My motive to practice is to explore the Self. I'm trying to hold back my expectations because they can be obstacles.

It's normal. Automatic breathing is shallow, and after a while, your body goes on automatic, even if you're consciously watching it.