A place to start that realistically requires nothing at all is exploring those specific feelings. If one "doesn't feel human", in what way does one not feel human? What things do not feel like they are expected to and what do they feel like instead? More importantly, what are they supposed to feel like? What are they supposed to feel like for humans? This does not even require a particular experience of any one type or any belief system or anything, this is actually a very common basis for methods psychology often applies. So keeping it grounded, for the time being, exploring those questions is a very agnostic way to help find one's issues and then find the root cause of them.
It isn't an uncommon experience for even mundane, perfectly normal people to feel like they "don't belong here [on Earth]" and that can vary from just normal behavioral issues, self-esteem and identity problems, and many similar. Not a single concept has capital on those alone and that is why it needs to be questioned extensively. One of the biggest reasons to do so is, is that if the answer ever is, "Just because it is." it is probably not the right answer and I will go so far as to say it isn't the right answer. None of these experiences, no matter their kind, stems from nothing; nothing does not produce something and something does not produce nothing. So it is absolutely imperative one is honest with themselves when asking about it. Allow me to add too, when asking oneself, do not shy away - there is tremendous deceit even within ourselves if we allow it and we will lie, handedly, to ourselves if we allow it. No, instead when asking why that feeling is and pursuing it, never once just accept the easy answer or the one that is the most comfortable, pursue instead that which is truth. This will, subsequently, prove to be quite difficult if one takes it to the extreme, but it needn't all be done at once.
Unfortunately a self-description only offers context and is, sadly, totally unreliable. It requires a substantial amount of trust that is already difficult to do in the physical world, never mind how much easier it is to get wrong in the digital one, and relies on an external force to make determinations. The process of discovering the true self and the nature of one's being is by virtue of its existence, an exceptionally internal and personal experience. This is not to say offering those things could not help, rather it is just saying it likely will offer little and offers just as much opportunity to make worse rather than better, if not more.
The single most important and best advice I can lend is that one reads and learns, remains skeptical, and plies questioning against themselves relentlessly, always asking "Yes, but why is that?" deeper and deeper until one hits the node. Do not worry, once it is struck it is fairly obvious.
