Is it weird for me to keep a diary/journal/whatever?

I find it helps me vent feelings, I can't stop. Ever since a was a little girl I've kept a diary on and off but I find I ALWAYS have to write my feelings down- mainly my confusion and grimness pretty much any feeling when I'm upset, but also when I'm excited I like to write and kinda doodle just a bit. For awhile when I got my first iPhone I stopped and I just started writing notes, but somehow my notes ended up piping up in my friends I phone in his note section i don't know how I guess the phone I gave him was connected by my Apple ID i don't know but it was happening so I stopped I've been hiding my feelings in a notebook and I feel very uncomfortable with the fact that if somebody finds it they will be able to read it so it makes me wonder- why the **** write them down if you don't want anyone to see them.
I've come to the conclusion that I simple can't stop writing but does anyone else do this. I feel childish keeping a diary, is it mentally unhealthy? Is it weird I'm 17 and am keeping a diary goin on Almost 18

I'm 17 as well and I have a notebook that I write a lot of my thoughts down in. It's not weird or childish at all, it's a really great way to vent if you don't have anybody you're comfortable talking to about your private thoughts and feelings. I mean, how else are you gonna get it out of your system, right? Just keep it in a safe place you'd assume nobody would find it. Also, if you trust your parents to obey your wishes, you could always write something along the lines of "please don't read, private." That's what I did. That way I know if my mom finds it, I know she won't go snooping through it.

Its actually really healthy and smart that you keep a journal to write your feelings. So they won't't pile up to make you miserable. And yes i keep a jounal also. But i don't write often in it because the thought of people finding it and reading it is so scary.