CRYING ON MY 16TH BIRTHDAY, WHAT IS WRONG WITH ME?!

So it's my 16th birthday right now and I'm sat here crying my eyes out and the main reason is because of my bitchy personality towards my parents.
They have given an amazing present (a gopro) but because it wasn't what i orginially asked for (a new phone) I went into a bad mood the whole day. My parents became tired of me so decided to return my gopro and get me a phone.
I feel so ungrateful and like I'm the worst child in the whole world. But I didn't want to act this way, it feels like something is controlling my personality because I say I want to stop being a ***** but as soon as I face my parents I start acting like one again. It has happened in the past and that's why I always dread birthdays. Is it just me or do I have some sort of a mental issue? I'm sorry if it's confusing but I need to know because I want this to stop.

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