You can start taking some lower bowel formula which will come through in your milk. You can also give the baby some Kid-e-reg directly, which is the LB in a glycerine-based tincture. Because of the tumor at the base of Kaylee's spine, the muscles which help with bowel movements are stretched out and don't work very well, so I use the Kid-e-reg in her bottles quite often to make sure she has regular bowel movements.
As far as starting solids - I usually recommend starting around 6 months - unless they are extremely fussy and acting hungry before then. I start with fruits because they are easy to digest. Kaylee is 6 1/2 months old and I just started her on some fresh, organic applesauce.