Why are you trying to stay invisible? Maybe there is someone out there who needs you to reach out to them, or even more important, maybe someone is praying to find someone they can reach out to. The Lord established this Church to help us to return to Him. He did it because He knew we all needed others in order to make it. I commend you for returning to church, but my advice is to find your Bishop and talk with him. Don't just go to church, be In the church. There is nothing better than having a good support system when you are trying to make changes. As for fasting, it is the feelings that count more than the specific dos and don'ts, but you should try to abstain from food and water for 24 hours. Good luck to you.