IBS-C or CIC is challenging. I was taking two Sennokot every second or third night and started to be concerned that because it's a stimulant it might be aggravating my arrhythmia. Switched over to Milk of Magnesia (every third night) around 2 tbsp. Will see if the excess magnesium does anything heart wise. Filled a script for Linaclotide but can't bring myself to take it yet.
Have you tried the safer over the counter osmotic laxative Miralax? It worked for me for quite a while. Also one gastroenterologist recommended taking Miralax everyday in addition to psyllium powder stirred into a glass of water Did that around four years ago and it works but caused other IBS symptoms.