I Am 62 Year Old Having No Stomach Related Problem

I am 62 year old having no stomach related problem till this time every time I have constipation with in two days recovered. This time it prolonged for more than 20 days Initially started with rantag tablet then Magaldite Simethicone and tranquilizer later gastroentrologis prescribed Rifagut, Lesvride, Razo.

I have normal appetite, my weight is constant , working normal, feeling like to take food but fear of belching and gas consuming lesser amount what are the tests required to confirm the trouble is it possible related to galbladder stone,