Can AGA cause excessive shedding?

AGA can certainly cause shedding but what you describe is more shedding than what is typically seen in AGA. In other words, if you do have AGA, it's likely there is something else going on as well. AGA is generally a slow process with shedding only slightly increased. AGA does not regrow on it's own (spontaneously). 

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 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 HAIRCHECK test will determine the Bulk Measurements of your hair and put a number on that hair loss (a metric) 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.