Feeling down

Hey guys.
Like the title says, I'm feeling waaaaaaay down right now.
It's just..lately, my relationship with my gf is kinda hard right now.
I know it's my fault all the way.
Why?
Because I jealous too much.
It all started when she told me that a guy called him.(lets call him Mr. P)
So, then I wondered, why the fuck did he called her?
Why didn't she told me earlier?
Then, things starting to mess up in my head.
Thinking that they might be having something.
But then again...
So 2 days ago I took her to get some dinner.
As usual we went to Nursa, Laguna Merbok.
We talk like normal but then, I saw her deleting something in her phone.
I don't know what it is until now.
First time I saw her doing that I ignored her.
But, the second time I asked her, she told me she's deleting some pictures of her cat.
I believed her because I saw it.
Then, I took her phone and pretend to check her pictures , songs and videos.
My real intention was to check who called her and who she called.
Then as soon as I checked it, my hands were like....I don't know...
Guess what I saw?
Full of Mr.P.
Missed calls, received calls, numbers called.
Yes!
She called him back!
WUT DUH FAAAK?!
I'm her BOYFRIEND and she didn't even call me!
I think I'm gonna cry right now.
I really do.
I know they have been friends for a long time.
Long before I knew her.
I know that guy, Mr.P, likes her too.
But...
That's it.
I can't write anymore.
I'm just sad right now.
See ya.