EXCLUSIVE

Trump Tower's been inundated with bomb threats since Donald Trump became President ... and it's become a giant pain for the NYPD and Secret Service.

Law enforcement sources tell us NYPD's been getting an average of 3 bomb threats a week since Trump got sworn in ... and many if not most of them are coming from the same guy.

The NYPD, Secret Service and building security sweep the building each time ... complete with bomb-sniffing dogs. If a dog zeros in on a person or a bag, law enforcement checks it out.

So far, nothing has turned up, and it takes a lot of time and resources.

Law enforcement will only evacuate the building if the threat is deemed credible, but there have been no evacuations yet because the threats appeared hollow from the get-go.