What else can I do to get the abs I want?

I run 2 miles 4-7 times a week. I do 50 crunches. I do leg lifts. Push ups. I curl weights. I drink only water, milk in the morning for some protein. I just started taking these Fiber Pill things. I weigh in the range of 134-138. I am about 5'8" maybe a little more. I am 16 almost 17. When I started the quest for abs I weighed about 158. I lost a lot of weight. And now it just seems I can't get the abs. I am stable at the weight I mentioned before. My mom and dad said I am getting to bony. But I still can pinch a little stomach. When I flex my ab area I have a strong top area, though my lower abs are weaker. What can I do to get my abs to show, and what can I do to get my lower ab region stronger like my top region? I was told reverse sit ups or crunches, I don't remember what they are called.