Does dietary cholestrol determin blood cholestrol level. If so, why eating 7 whole eggs eveyday not increasing my cholestrol level.?

Yes. Dietary cholesterol is but one of the factors which affects cholesterol level. If it is not affecting yours, your are lucky. Your liver appears to be processing it well or you may be on powerful statins which may be keeping it down. I would check with your doctor to be sure consuming so many eggs is right for you (perhaps if you are a body builder or high intensity athlete).
Poor diet affects it. The primary factor that affects cholesterol is genetics; your parents play a greater role in your "fasting" cholesterol that does diet. However, a diet high in cholesterol may not greatly affect the "fasting" level but it certainly raises your "peak" cholesterol level, the the highest level your cholesterol reaches throughout the day. Unfortunately, this is something we don't measure. Eat low fat.