In addition to what GeryM said, I'd like to break down some symbols in additional ways here. As he said, "Only God can give you the answer.. the revelation of the Holy Spirit must bear witness with your spirit."
I am lying in my bed in my room
Your bed is often the purest form of ownership -- something that is only yours in your house. Your relationship with God, mentioned above, is one good example; another might be the essence of who you are -- your dreams, goals, your ability to decide...things you don't even tell other people.
about to sleep,
Rest without keeping watch... blind trust. Relaxing, pausing, renewing yourself. Retreat.
I notice I'm surrounded by a group of people, I'm not sure why.
Imposition-- how rude. It was your territory, completely, and others imposed themselves without asking or even telling you why they were there. You needed rest, and they prevented you from feeling relaxed or having a safe repose. You were left out of your own loop.
Before going to sleep I decide to sleep on the ground instead,
You gave in. Subjected yourself voluntarily. Assumed others had authority, or a louder voice, and you didn't want to fuss with opposing them.
one of the people sleeps in my bed.
Yielded your spot to another. The most precious, private thing you could hold onto was given up. Look back at what was said above, and reflect also on whether someone has talked you into going to a different church, or gained popularity in a tight circle of friends, or taken over your responsibilities at work.
The next morning that person is dead, and I realise God saved me and I thank Him.
This reminds me of the story of Passover. The Egyptians used to honor their oldest children by keeping them at a certain bed level. According to some theories, noxious gases/CO2 from magma in the water rose onto the land and suffocated anything breathing at a certain height. All the firstborn of the nation died.
Lake Nyos Disaster
HowStuffWorks "How did Lake Nyos suddenly kill 1,700 people?"
The Hebrews had humbled themselves by following God's instructions that night, and were spared. God knows what we need, even when it doesn't make sense.
The next night,
Notice the different time period -- it can be important in showing phases.
I'm in my bed again and I realise there's a man outside my window, trying to get in.
A manipulative, secretive intrusion. The last people boldly and publicly showed up, but seemed safe. A robber is sometimes armed and scheming, so presents greater potential danger.
He tries to get in again at the bathroom window.
Another private place, but one you'd even be less inclined to invite people in. Sometimes embarrassment associated... so look at areas of yourself you don't like to talk about-- habits, hurts, things that need restoring but you're holding back. Family history, bullies in your childhood.
Some people also dream of a bathroom as a place of cleansing and refreshing. If you applied this to your spiritual life, for instance, it could show a prayer group or worship itself. Whatever renews you. Being threatened.
I run to my parents bedroom and the three of us start praying as we know he's coming.
Yay!
I am curious about this part... what the parents represent. It might be strong Christians that you trust, youth leaders, pastors... but could be more conceptual and broad. In any case, your solution was prayer instead of calling the police or shooting him. Did you notice that? Most people's dreams are more violent. Good move!
I remember specifically saying "We will die worshipping in the Spirit." I was praying in tongues.
You took charge and leaned on God, instead of your own strength. When you show yourself humbling yourself in the first part, it could seem you would be overpowered. But you wrestle not against flesh and blood ... you can survive just fine without human strength, when you rely on His strength residing within you... His mighty power from Heaven.
A few nights later I have a similar dream, except the man enters my room again and begins stabbing me. When I look at his face, its my brother.
http://studylight.org/desk/?query=mt+10:21&translation=nas&st=1&new=1&sr=1&l=en
Mt 10:21
Brother will betray brother to death, and a father his child; and children will rise up against parents and cause them to be put to death.
I think of this when I hear news on home-grown terrorists... normal people who live among us. But this can also apply to Christian brotherhood that worships with us, attacking without reason.
Your brother is like a piece of yourself... a partial reflection of who you are. You can despise him one day and appreciate him the next, but you know he will always be there for you in the long term.