What Causes Frequent Bowel Movements?

Hello, I have a persistent problem with my bowels. I’m not sure how to describe the full extent of the problem but it appears to me that my digestive tract doesn’t process what I eat well. I don’t suffer constipation and not too much diarreaha (occasional). I occasionally have urgent need to go episodes but less than once a month. My problem is that I need to go multiple times a day and the amount of fecal matter is seems to be large (fills toilet bowl to water line). I often don’t feel like I have totally eliminated and need to go again within a short period of time. I have tried digestive aids to no avail. I know that a portion of the problem is that I over eat on occasion when I’m physically tired. I know that I have multiple food sensitivities to milk, gluten, mushrooms (molds), and soy, which I avoid. In addition I have a fairly rare condition where my liver doesn’t methylate enough B-12 to meet my needs despite the fact that there is plenty of B-12 in my blood. I suspect that this exacerbates the hunger when I’m physically tired, I suspect something is wrong but I don’t have any reasonable ideas. This doesn’t seem similar to anything I’ve read about. Any ideas?