My leopard gecko has not been eating well for awhile now. The silkworms are ingested but come back out overnight and do not appear to be digested. There have not been any bowel movements happening either. Switched to crickets and they often disappear but again there are no bowel movements. His tail has started getting smaller recently. He is on a sand substrate. Not sure if there is sand impacted or not. Again this has been ongoing for awhile. Any suggestions as to what is happening and what I should do would be appreciated. Thanks.