Suggest Treatment For Heart Palpitations And Constipation

hello doctor, i had palpitations problem for 2years last month after diagnosing doctors concluded that i m having vasovagal syncope due to IBS, my doctor prescribed me Rifagut 400,O-anxit,betagrain 40tr,opiprol 50.i never had constipation problem in the past but after using the above tablets i m having severe constipation for which i m taking dulcolex tablet once every two days.i told my doctor about it but he said it is due to ibs.i m taking fruits,i m taking enough water but i m not getting rid of this constipation.i never had constipation problem so can you tell me what might be the reason for my problem? does the above medicines cause constipation? is there any side effects if i use dulcolex for longer periods?