What are the factors that determine whether a person may/may not lay Tefilin.
What would the din be in the following circumstances:
1. A person has a windy stomach but has no need for the bathroom.
2. A person experiences stomach pain
If a person has a ‘windy stomach,’ and is unable to refraim from occassionally passing wind, it is forbidden to lay tefillin.
However, if a person has a stomach ache, but this does not cause him to pass wind or require him to use the bathroom, the pain would be no different from elsewhere in the body, and it would be permitted to lay tefillin.
Sources: See Shulchan Aruch, Orach Chaim 38:1, who writes that somebody who is a choleh me’ayim, meaning one with digestive problems, is exempt from wearing tefillin, the reason being (Mishnah Berurah) that tefillin require a guf naki, a “clean body.”