You have plenty of muscle down there, you just need to find them and work them. There are physical therapists who specialize in pelvic floor therapy. A lot of women can't find their muscles down there. The physical therapist can help you find them and give you exercises to strengthen them. Strengthening abdominal muscles can also help, as well as maintaining a healthy weight. Please mention this to your family doctor next time you see her. She can make recommendations and give a referral to a physical therapist too. Your doc may just say "do Kegels", but since you've tried to do these exercises many times before and feel you haven't done them successfully, a physical therapist seems a good route to go. To find PTs on your own, go to this link, and click on your state in the map:
http://www.womenshealthapta.org/plp

Good luck.