Sentence 1: Bridget as always sleepy. 
 Sentence 3: No matter how early she went to bed, Bridget was still sleepy 
 Sentence 4:  Bridget started taking melatonin at bedtime 
 Sentence 5:  Bridget started sleeping better so she wasn't tired 
 Option 1: Bridget tried going to bed early. 
 Option 2: It was because she kept staying up later and later playing video games.