This can be caused by gas, you can should be able to breath better using chest breathing instead of belly breathing. While belly breathing is touted as being superior to chest breathing, there has been no rigorous science done in this area. Some results suggest that there may be some health benefits for patients suffering from asthma to practice belly breathing. Arguments like chest breathing being a lot shallower and therefore bringing in a lot less oxygen is pseudo-scientific nonsense, you can run just as fast with either breathing method, unless, of course belly breathing is obstructed by e.g. excessive pressure due to gas.