Hi There, I Am A 6 Year Long IBS Sufferer

Hi there, I am a 6 year long IBS sufferer with Chronic Constipation (26 YO Male) which I manage with daily laxative use (mostly Lactulose). My questions is that from my own experience drinking a lot of warm-hot water after Lactulose gets me a nice diaheria like movement about an hour later. My problem is that shortly after release I get extreme distension and a little bloating and it looks like I am pregnant and swollen even though I feel relived. So I take some more Laxative and same results 2 more times (in same day). I suspect that the Distension is the Water and I want to know how I can rid it quick (is diahretics my only choice). The Problem is even after the 3rd time their Is still watery brown waste coming out so how do I know when my Bowels are empty as it feels like I have rid a lot and by the third time I am feeling weak and tired and Ill until drink a sports drink or sumthing. Basically I can manage the Constipation but not the after effects of the laxatives and when I take less I get no relif. Any thoughts?