hi ivan
yes, practicing some types of meditation and watching bright lights does decrease melatonin secretion, and cause difficulties in falling asleep. i used to have such problems previously when i was learning “art of living” pranayam. it stopped when i stopped doing such things.such meditation, etc are meant to be done in the morning when u wake up. taper off slowly whatever doing and remove crystals from ur bedroom (temporarily) till u get back to ur normal sleep pattern.. also cut down on coffee tea from 4 pm onwards. you will get good sleep at night.
good luck.