I think the problem with low carb is that unless you intend to do it forever, your weight will probably yo-yo (it has for most of the people I know who have tried to just “eat normally” after low carbing, unless they switched permanently to gluten free + sugar free or calorie counting or something else permanent to take its place).
You mention you eat the wrong things and drink too much, so it’s maybe the type of carb? Could you perhaps just eliminate some things from your diet and try that way? Because all carbs are obviously not created equally. Your bowels should not be suffering because there are too many carbs in fruit or vegetables, so you lower them, too. Maybe cut out refined carbs (no pasta, white rice, bread, alcohol? All not great things for IBS anyway) six days a week, give yourself one day off, and don’t count carbs in your five-a-day (though obviously don’t go overboard on things like dried fruit that are loaded with sugar).
Or you can look into carb cycling? I’m not sure of your body type, but if you do well in low carb, and gained weight without it, you may be an “ectomorph” (I honestly don’t know if this body shape ‘science’ is complete bollocks BUT they claim that shape needs to eat only 30% of a daily diet in carbs, instead of 50%, unlike tall, naturally lean types, and will gain weight if carbs make up 50% of your daily diet apparently. I’ve just been reading about it but something to consider).
I would just say, before you start this time, maybe consider something you could live with permanently, so you don’t just low carb, lose the weight, then gain it again after all your hard work.