I'm 17 year old teenage boy who is experiencing hair fall and hair thinning! What do you think is happening to me?

What you are describing can certainly be due to genetic pattern baldness. Although your current family and relatives are not showing signs of hair loss, the genes responsible for androgenic alopecia (i.e. common baldness) can certainly skip generations.If your condition is not due to genetics, it is possible that your hair loss could represent some type of telogen effluvium (i.e. temporary hair loss caused by bodily stress). The stress can be due to events like surgery, or even what people might consider to be psychological. Stressful life occurrences can exert an influence on neurochemicals which may affect the hair follicles.
The best step to take would be to speak to a doctor and get a diagnosis. This will help you understand which course of treatment would be relevant to your situation.

If you are losing hair want to know why, it is best to see a doctor for an examination because as you rightfully point out that looking on the Internet will only give you "theories and intelligent guesses".

No one belittles the loss of hair and how it can affect anyone, especially at a younger age. Our hair changes at some points in our life due to hormonal changes in our body,. This is a natural occurrence and settle down over a period of time. There are many causes that can increase hair shedding if that is the case. A change in the natural growth cycle causing the hair to shed the follicle prematurely, creating the imbalance in the growth to dormant phase. We normally have around 90% of our hair visibly growing. Before any signs of actual thinning it can take a high % for this to become noticeable. It would be prudent to visit a specialist if you are this concerned and maybe have a diagnostics check.

There are multiple causes of hair loss which cannot be treated without proper history and physical examination. Thus, it will be better for you to visit some hair specialist and get a proper treatment from him to solve your problem of hair loss.

Hair Loss can be a traumatic experience especially in one so young. I would advise you visit your Doctor and speak with a Dermatologist to seek a professional opinion from them at this stage.

Hair loss is a scary experience, especially when its hair loss at a young age. Chances of hair loss while you're in your 20s is in the 20% range, but seeing how hair loss doesn't run in your family, it'd be best for you to consult your GP. Losing bulk amounts of hair is concerning for sure, so see your family doctor as soon as possible. 

This is a common type of Androgenetic Alopecia, unless there is a medical history of hormonic disease which is rare. We expect excess hairloss in young ages until the 30s therefore it is extremely important to receive conservative medication (such as minoxidil) and address a plastic surgeon or hair restoration expert to advise you.

You can get a final answer on the cause of your hair loss by seeing a dermatologist or other scalp specialist and having a full hair and scalp examination. Blood tests will likely be needed based on the information you have provided. In rare circumstances, a biopsy will also be helpful.This is the only way to properly diagnosis hair loss: Full medical history and clinical examination followed by supportive testing if needed. 

Have you seen your doctor about this, or a dermatologist? That's the first thing to do to get a diagnosis. Without that its very difficult to suggest a treatment. Alternatively, you can send good photos to a specialist. I do get young men with hair loss who, like you, cannot find an obvious member of their family with hair loss.The most likely diagnosis is still male pattern hair loss I'm afraid. If this does get confirmed for you, then start Minoxidil and/or finasteride asap and review after a year

Your biggest enemy is the progressive
thinning leading to a balding pattern that is not evident at this point in
time. The degree of thinning that you are experiencing would suggest that
you should see a doctor who has a HAIRCHECK instrument and will most likely will get
Bulk Measurements of your hair to determine the degree of the thinning
that you are presently having. If the diagnosis is early genetic hair loss
(the most common cause of hair loss in young men), then the best treatment
would be the drug finasteride which is highly effective in men of your age
and may not only stop the hair loss but possibly reverse it. If you are
developing a more advanced balding pattern the best test to get
will determine the Bulk Measurements of your hair and this will show, over
a one-year time frame, how effective the treatment will be. Once you know
this information, then you and your doctor need to develop a MASTER PLAN
which will define what you need to do over the years to come.