Please seek immediate emergency psychological care. Even though it doesn't feel like there is a chemical problem going on, and it just feels like the situation is what is causing causing your sadness, there is allot that boosting chemicals in the body can do to change your outlook; during this time you can work through, in a much more productive manner, all the things going on in your life with someone who will listen to you in-person(an important aspect of our psychological care). A psychiatrist/psychologist can help you step back from the brink and get the more balanced side of you to do some talking. Then spend some time with some other people who can help you with wider view of things as well(in person): a pastor/theologian, an older wise person who has been down a similar road, a college professor who is willing to lend an ear, or reconnect with a wise old friend(not just some joker). Do not continue in the endless loop of your own catastrophic thinking. Reach out. Break free. And don't stop.