Don't take it the wrong way...I'm asking you to stop suffering, get free from this hopeless chain, your children are teenagers now...they should understand. Get a new life! Your kids will be fine!
I'm a teenager, and my parents have been together for over 20 years as well, and get along 'OK'...but if they were to divorce, and I'm telling you the truth, I wouldn't really mind THAT much...they aren't kids anymore, they should understand.