Why do I find it hard to make decisions that are a true reflection of what I want?

Thank you for your question in relation to finding it hard to make decisions that are a true reflection of what you want. 

It feels as though in order for you to be able to move towards decision making in a way that feels authentic to you, you would need to perhaps challenge some of the thinking patterns that you have developed over the course of your life. 

Negative Automatic Thoughts occur whether we want them to or not (because they are automatic), they can often feel out of our control. They are essentially electro-chemical impulses within our brain, not actual facts. It's important to remember this. Our response to the thought (impulse) is based in our emotions. This in turn can then affect our behavior. An example of this is that you have used in your question is found in how you have an infinite amount of thoughts, that lead to you feeling like a fraud, which then leads to you not making decisions that align with your authentic self. 

With plenty of practice, it is possible to begin to reframe our thinking and our thoughts. It doesn't necessarily stop the thoughts from happening, but it focuses more on changing our response to the thoughts (emotionally and behaviorally). You can do this by challenging the thoughts that you have and seeking alternative meanings. Is there evidence to support the thought? How else might you see the situation? Are there alternatives to your current thinking? etc. There are things like thought records that can help with this. I suppose one of the key things to ask yourself, in this instance would be: 

"What do I want?" "Is what I intend to do, authentic to who I am?", if it isn't what you want or authentic to who you are, then ask yourself "do I still want to go ahead with this?" This will support you to recognize where you do have control and if you are making a conscious choice to do something that doesn't align with you authentically, or give you an option to change your course to be more authentic if that is your preference at that time. 

It sounds like there is a lot more to unpick, but these are starting points for you to look at and of course, we are always here, if you have further questions or require more direct support! I hope this has been useful!