Why do I keep dreaming about random things from the past?

Lately, I would say the past 2 weeks or so I keep having dreams. I never remember my dreams ever, but these I can remember very clear. The 3 I remember the most vividly all surround around things from my past and odd things is each one keeps going deeper and deeper put bringing elements from my past to the future. For example:

Dream 1: Involved my last roommate and we moved into a situation that we would both normally never live in. I have not talked to my old roommate in months though and when we moved in we both had futons as our beds which I had for a few years as a teenager. The living arrangement was with one other guy and he was very odd, enough to creep me out a little and the apt got darker and more broken down as the dream went on. Then I woke up kinda freaked out.

Dream 2: Involved my ex GF which I haven’t talked to in months(dated years ago) and she was actually some kind of famous person and I was going with her to some kind of event but it was very toned down to my normal attire that I would wear now and felt like it was at my current age. This dream was kind of funny but I woke up feeling a little odd for some reason.

Dream 3: Involved my mom and living in our very old house(actually it was rented) The house was a transition to my parents buying there own house and was very very small.
I walked into this house to find my mom, grandma, and aunt all sitting at the table and I was like what is everyone doing here, we don’t live here anymore and my mom shrugged. More bizarre I haven’t talked to my grandma or aunt since my dad passed away 3 years ago. I haven’t thought about this house in over 7 years never mind seeing it. I walked through every room and as I walked into each room it was like waves of memories from each room came back to me(placement of furniture etc.) (except the bathroom had things that an old woman would use and I thought they belonged to the person that currently lived there) My dog that I have now was with me and as I walked out of the bathroom my mom was the only person in the house and she was getting ready for bed. We exchanged words about where the person that should be living there was and my mom said that in this town you can come and go as you please but in a really odd manner then walked into the bedroom.
Here is where it gets weird, I walked downstairs and my dog followed. The basement was set up slightly different then I remember and there was wooden stairs leading into the dark of what looked like a room being built in the basement that was set up from the floor. I walked up the stairs and pushed the door open. It was pitch black and then I could hear what sounded like a door in the back of the underconstruction room and someone walking on the floor board past that room. They were walking slow but steady and my dog went to run in. I grabbed him and went back upstairs and just saw my mom standing there listing up at the ceiling. I looked at her (at this point my heart was racing and I was kind of scared) We both looked at each other and I said mom what is that, there is someone up there, and then I woke up.

Sorry for the long descriptions but I thought they might help. The weird part is all 3 of these dreams had me wake up in fear to an extent or an extreme state of confusion. I never ever remember dreaming and I certainly don’t dream about things from my past when I do. Any ideas why this could all be starting? Also from Dream 1 – Dream 3 they keep going further back in time.