2 year old hasn't had a bm in 4 days complaining of pain and crying what can I use 4 fast relief? She in pain

Laxatives or enemas. ...Are safe if used once in a while, but not if used frequently. For fast relief, a pediatric fleets enema or oral milk of magnesia (magnesium hydroxide) work quickly. For repeated constipation, her doctor can recommend diet changes or a stool softener, but these won't work as quickly to relieve pain.
Fast relief. You can either use a glycerin suppository or an enema. Once you are over the crisis you need to modify the child's diet by reducing milk and milk products, increase fruis, vegetables, legumes and nuts. Also use high fiber cereals.