Is it normal to feel like theres two sides to yourself?

Yeah I'm the same way.
It sucks. I had a Dr instantly tell me i had MPD (multiple personality disorder) but family says other wise and i have control of all my actions. That's just what happens when you show up to an appointment sleep deprived and detoxing.

I feel like that a lot too. I'm usually very sweet and gentle towards everyone, but I also have a nasty dark side that comes out whenever I feel angry or jealous. I even do the whole "trying to make my friends hate me" thing too, which I think has a lot to do with trust issues (in my case anyway).

every one has two halves to their personallity, mine are both eccentric and a little dark. but it depends on who you are.

Body dysmorphic disorder. Cyclotimia. Obsessive compulsive disorder. Look it up.
"I sometimes feel like my actions are out of my control"
I know somebody who has the same trouble but never actually considered the possibility of being merely locked in a loop of automatic behavior.
You might wanna avoid saying sentences like the one above. People would just assume you are loco.

I am deciding to change these letters! I am in control of my own actions! Or not.

This is a tricky one that I'd ask for more context on, but it kind of sounds like you're having bouts of self doubt or depression. If you're in a stressful situation, it wouldn't be terribly odd for your mood to swing after a hard day, only to turn back around after you've relaxed.

If you really feel like you're losing control, though, it might be a good time to investigate the matter further, possibly with a psychological expert. But again, not sure about your situation, could just be stressful times. It really depends on where you are in life and what you're doing right now.

I think everyone to a point has two sides of their personality. It's kind of like the angel and devil that sits on your shoulders kind of thing (it's hard to explain).