Few Questions?

Is it possible to have a more then one dream in 1 rem period?
Becouse i woke this morning about 6 and didint remembery any of my dreams.I went to bed again 5 minutes later and was asleep for 1:30-2:00 aprox. Then when i woke up i rememberd 3-4 dreams.Where all of them from 1 period or i rememberd the last one.Anyway all of these dreams contained one thing:me carring a BIG keyboard (?). So maybe when i remembered 1 dream it triggered others ( since they had simillar contex ).

Another thing yesterday i was taking a short sleep during the days 1hour or so.When i started to go to sleep i was thinking about my old dreams and lucid dreaming...and suddenly i felt like i was approaching to somethig white like wall(?) , my heart started beating fast , my breathing got out of loop , and eyes were moving strange , i got little scared , then like something suddenly droped at me, my every muscle moved i was just like i jump of bed.Well im sure it wasnt dream becouse i hit my head to the wall next to me.