Garlic and onion are high in inulin, which is generally bad news for IBS. You may have a threshold level you can tolerate. Asparagus is a less concentrated source of inulin. Suddenly increasing vegetables in general is likely to give anyone constipation. If you did the cleanse, you may have slowed down your metabolism, which would be another explanation. You could try eating more calories more frequently throughout the day with slightly reduced fibre for a while to see if you can reverse this.