Dreams after meditation

Dear Dhananjayji, i hope you are progressing well in your sadhana and i sincerely thank you for your guidance in our spiritual pursuit. I have been doing meditation in two sittings-morning and evening for the last few months. Since i was fascinated by the results of meditation, recently I decided to start third sitting just before bed time to hasten my progress on spiritual path.But now I am experiencing vivid dreams and nightmares during my sleep.This has created doubts in my mind. Please guide me should I continue to meditate just before sleep? And kindly explain the reasons of vivid dreams and nightmares because of meditation, if any.