What I did was... Sing everywhere I went. If I took the notion out shopping, or in work I sang. Sometime easy sing talkng volume, other times full concert belt it out volume. I just decided that I needed to get over myself and if people didn't want me to sing they would say. Sometimes I would get strange looks but mostly I hot a good reaction.
It's all about confidence, and much of that is getting used to people looking at you. So my solution was a baptism of fire. Get used to as many people as possible looking at you singing, and you will get over it pretty quickly. Avoid too long a period between you being seen singing. By that I mean even 20mins is quite long.
Additionally, take every opportunity you can to perform your songs, in front of family, friends, the band. Don't be timid, make your mistakes loud and proud. The more you do it, the more confident you will get, the more relaxed you will get and that will allow you to focus more and more on performance.
As a frontman get used to singing with your eyes open. Pick a few specific people to sing to, and sing to them! It makes for a more convincing performance.
Practice over and over and over. Get so familiar wit the songs you can do them in a hurricane without losing focus.