You must excuse me for ignoring the part about you seeing UFO's or your roommates friend being abducted as I believe this has nothing to do with your dream.
First you say that you do not dream. People most of the time dream while being in REM sleep. (Rapid Eye Movement). This is a stage of sleep where your brain activity is the highest, this comes along your eyes rapidly moving horizontaly, thats where the name comes from. During REM sleep your brain activity is the highest, and these are the dreams that are the easiest to remember, especially when being awaken by your alarm clock for instance during REM sleep. If you awake during your REM sleep you will most likely remember your dream. But when you dream during another stage of your sleep the chances of remembering it are much much smaller due to less brain activity. This is an explanation why you do not remember most your dreams.
Dreams can also be very realistic. It is not rare that you can even smell things in your dream. Clearly you woke up during your REM sleep, because you can remember everything so clearly. You woke up still having that dream in mind and saw your ex-boyfriend but when looking again you saw your current boyfriend. This happens quiet often and it is nothing that you should worry about in my honest opinion as you do not mention that you have sleeping disorders or suffer from sleep paralysis.
So its just a normal dream that you remembered a bit more clearly in my opinion.
Among His proofs is the creation of the heavens and the earth, and the creatures He spreads in them. He is able to summon them, when He wills.