Is my site being attacked?

The CI Cart Class uses sessions for keeping track of all the items etc;

Hello InsiteFX ,
At first I'd like to say thanks for your help!

In my website:

1.What did you Try? What did you Get?
In the past (from 2015->June 2016), I used default config [[$config['sess_save_path'] = NULL;], my site worked normally. User can browse site & buy products (from 2015 to June/2016).
However, since last week (9th, July), I can NOT browse my website, It's a white page (Blank page) without any text, images...

After that, I try to changed my config into
         1.a : First I used this config: [$config['sess_save_path'] = 'ci_sessions';  $config['sess_driver'] = 'database';] & created a table "ci_sessions", I saw that a lot of sessions record were inserted in to database. It seems that They were written automatically as a robot ( about 2 records/ minute, I sure that mysite does NOT have a lot of users).
 
    1.b:  Second I changed to this config:   [$config['sess_save_path'] = 'ci_sessions';  $config['sess_driver'] = 'files';]. With this config, I saw that there had a lot of files ci_sessionxxxxxxx were generated in public_html/ci_sessions folder. They were also generated automatically as a robots too.
 
Now, I use config (1.b), today (14th July), I deleted total over 400 ci_sessionxxxx files (in folder public_html/ci_sessions). I'm sure that my site does NOT have too much user as that number.
 
I have a function to count "Product detail view" every time user opens a product detail. I wrote this count into database, & I see that this number is being increased very fast (Today (14th July), in the morning (~7:00 AM, totals views is 2862, but now (23:43 PM) it is 3544 (total views))  

I think there have an automatically trigger (maybe from inside CI or maybe from outsite website(hacker) ) try to call my site with a frequency.

2. What did you Expect?
  Mywebsite (www.hotfashion.vn) is in a normal site that shows list of products. User can view product detail & buy it. When they by a product (or many products), I store it in Cart.
  After that user goto a form to input some basic info (UserName, Phone Number, address). Then ending a shop tour ( We DO NOT have payment  directly via Visa, Master card...).
  The shop will call to this user to confirm the order & delivery product to him/her. He/her will pay cash for Shipper.
   Currently, I DO NOT keep track users. (Maybe I'll add in the future)
  
  So, could you please help me what did happen that I can not use old config (from 2015->June2016) [[$config['sess_save_path'] = NULL;]? (Blank page if I use it)
      Now I'm using config (1.b) above (or change to (1.a)), Can I stop generating the ci_sessionxxxx files (And sure User can buy products)?
  
  If you need any more information about my code/web, please let me know!
  
I'D LIKE TO SAY THANKS A LOT FOR YOUR HELP.