Question about cholesterol levels?

I got back my cholesterol results and found the results kind of strange. My doctor told me that I don't need to do change the levels and they are fine, but I disagree, and would like your input.  

The Triglyceride level was "low": 0.55 mmol/L, where 0.60-1.70 mmol/L is considered normal.
HDL was considered within "normal" range.
LDL was considered "high": 3.36 mmol/L, where 1.70 to 3.00 mmol/L is considered normal.
Total Cholesterol was considered "high".

My question is should I listen to my doctor's suggetion, which is I don't need to work on lowering or changing anything? Did the doctor say this because my TRIG levels are low? But that leads to my other question - how is it possible that on a mostly fast-food diet and no exercise my trig levels are low? And is it normal to have a high LDL but low TRIG? Aren't they correlated?  
(I am a 28/F).
Thanks!

[ed34]

well in the UK the base line for LDL is 4.0mmol/L so I would be happy with 3.36. It used to be 3.0 here but it was raised due to very low levels causing memory/mental issues with quite a few patients.