I rethink a bit, it really could be a combination of several factors:
1: playing with toys/porns (for training but still wrong,
https://www.fleshlight.ca/collections/fleshlight-girls/products/riley-reid) for quite some time, mess up my brain, much more intense than the real things at least for me, it's like you been taking cocaine for quite some time, now you start smoking cigarettes, of course, you feel less excited ...
2: psychological issue, because I did not have any real sexual experience 1 month ago, too few encounters, over-thinking cause anxiety(HIV/STDs, .etc).
3: I think the medicines I've taken really account for 60% of the causes. I am taking them to increase my productivity at work and off-work as well, those medicines really helps me perform well at work and in other scenarios, obviously, that comes at a price, those meds significantly reduce my sex drive, I guess that makes sense, if you are sexually aroused, you cannot focus, if you cannot focus, you cannot be productive...