I think perhaps your main problem here is simply not warming up properly. The voice doesn't function properly when you start the gig, so you're troubled by that and don't perform well, which worries you, so next time... etc., etc. If you're going to take lessons in anything, I reckon you'd be well served by a good singing teacher who will, in short order, give you some sensible exercises to warm up. A medical check won't do any harm, and may help the confidence. Alexander was an actor BTW, and his successors have a habit of charging an awful lot of money to enlighten you. That isn't to say it doesn't work - lots of musicians have found it helpful - just that it's very costly. Good luck.
KYBTTS