The Other Side Is Watching Me, I Can Feel It

I gained a new ability that I been having for a few months. Ever since one of my best friends died (not saying how, that's private only to my knowledge), I could sense when someone or something is in the room. This is also the moment when I became a medium. Recently, I experienced something that I did not know before. Actually, a couple that I want to share now.

Six months from now, my dad bought this beautiful house in my neighborhood. I got a room across from my dad's office (he works from home). My room had a walk-in closet, which I always wanted. When I first walked in there, I did not sense anything bad there. But, around September, I felt something. I sensed that someone was in there, but invisible to sight. I then had a vision of who that spirit might be. It was a girl, about 7 or 8 years old, wearing a white formal dress, like she was at a wedding. Then I knew that she died in the closet, but her family knew about it and cleaned the closet up so nothing could be seen that could be led back to the death. That was the only time I saw her in a human-like form. From then to now, the only communication I can get from her is a flickering light and taps on my arm when I'm in bed. Sometimes, I can walk into my room and feel no presence at all. I can sometimes see where the sprit is located. A way that I tell her that I know she is there is that I say something that her parents might of said, like "Rest in peace", every time I close the door after getting something.

More recently, my mom's house also has some visitors from the "other side", that I could sense. A dog died by old age, and it is the guardian sprit of my little sister. It (I don't know the gender) watches over my sister when she is in our playroom

I would like some advice and help with this new ability. I would also like opinions about the following:

Should I practice this ability enough where I can sense more things? And if yes, what could I sense?

Is this a common ability?