It sounds like you have slowly allowed fear to be in the driver's seat. The thing is, confidence is built when we work towards something and find that we either meet a goal or find that failing to meet the goal wasn't that bad after all (anxiety is about negative anticipations about the future). Of course, if we are just sitting around wasting time then our anxiety is rooted in reality. Eventually, we reap what we sow so if we aren't tending to our "garden" by cultivating good habits like exercising, eating right, finding a job and sticking with it, or these types of important things that will payoff for us eventually then we may be anxious because our subconscious knows the outcome will be bad.

I recommend deciding on a managable goal then spend time working on that goal everyday--eventually, you will either succeed or realize you need to adjust the goal. Taking positive action can reduce anxiety and once you succeed at something--your confidence will grow causing you to be motivated to accomplish more. You say that you were once self confident. Back then, was there something that you accomplished? If there was--remember and focus on the fact that you have been successful before and, bit by bit, you can be again. Also, if there are people in your life who are discouraging--limit your time with them. Plus, look for a place to work or a friend that are encouraging.

How to Overcome Your Irrational Fears (That Stop You from Succeeding)