Why is my cholesterol so high?

My cholesterol is 208 (LDL is 128) but I am 24, weigh 146-149 lbs and eat salad for lunch. I know a lot of people that eat wayyyyyyyyy worse than I do yet they don't have as bad as me...could this be indicating something else. I am taking Yaz (birth control), Metroprolo (for SVT) and currently an antibiotic for my sinus infection. Any ideas? I have had fibroadenoma and that's it.