Slow website

I am having some problem with my website load up time. I have tested it 2 weeks before (on pingdom) and it had 1.6 seconds load up time. Now I tested it again and it had 12+ seconds. I have tried optimizing assets with hummingbird but to no success. I have checked server side settings and have no clue as to what may be causing this problem. The result showed me that the website first-bit connection is after 8 seconds which is very weird (how can it receive the first-bit so late?).
Does anyone have any clues as to what is my problem here?
All help is very appreciated also I have opened support access to the site.

Best regards,