There are many items that can impact website traffic. Most server measure this in Gigabytes (Gb)
Below are the common items:
There a few way to check your website, to find the page/s that are increasing the traffic.
If you are not sure, you may need to get advice off you web developer or request if they can run checks for you.
A target size would be between 500Kb and 1.5Mb per page.