Causes for increase in LDL cholesterol levels

I am a 41 year old male, 5"7' weighing 159 lbs. I have been having high cholesterol for 8 years now. In this period, the maximum total cholesterol level has been ~245.

I am not on medication except for a short period of time 2 years ago. My goal is to reduce my cholesterol by natural means.

My cholesterol levels in Jan 07 was (Total-221;HDL-45;LDL-147;VLDL-29;Triglycerides-143)

After 6 months of regular exercise and dieting/healthy eating my cholesterol levels dropped to the following levels in July 07 and both my doctor and I were very happy.

(Total-157;HDL-43;LDL-95;VLDL-19;Triglycerides-94)

Now after 7 months when I had my cholesterol levels checked again, my total cholesterol went up to 212 and my LDL went back to 145  (Total-212;HDL-49;LDL-145;VLDL-18;Triglycerides-89)

During the last 7 months I had continued on my daily exercise and healthy eating and maintained my weight at the same level as 7 months ago. I am not sure what could have caused my LDL to go back up by 50 points.

One reason I can think of is changing to Fish Oil omega-3 capsules twice a day compared to Flax-seed omega-3 capsule that I used to take in the first 6 month period. I read somehwere that Fish Oil can increase your LDL. Could this have caused my LDL increase ?

I have also been consuming nuts (almond, pecans, walnuts, pine) and seeds (pumpkin, soybeans, sunflower) along with Oat-bran for breakfast almost everyday. Can any of these nuts or seeds cause LDL to increase ?

Could this be due to a Lab calculation error ? Should I ask my doctor to have a lipoprotein analysis done to determine the exact LDL and HDL levels ?

I want to know if my cholesterol levels require me to be on cholesterol lowering medication ? How long can I continue with these levels without the risk of developing cardiovascular disease at a later age.

I would also like to hear about other natural ways to lower LDL cholesterol 

Please note that I now switched back to Flaxseed omega-3 capsules recently.

Thanks

Tsr