“Scared of ALS?”

Recently I’ve started experiencing strange feelings in my arm and hand after yoga training recently. My thumb gets stuck suddenly (usually after using it) in a straight position, as if fixed, and buzzes inside, but it’s not visible. After a few seconds, my thumb returns to a normal position and I feel again that I control it. Also, I have twitches in that arm and in other parts of my body, and my thumb and partly hand feel rigid at times and weak. When I straighten or bend my thumbs they also shake. My shoulder also aches a lit bit, because I’ve sprained it. I have a severe phobia of ALS and already had ENMG when I sprained my arm 5 months ago and felt weakness in it. I’ve also had ENMG two times before that because of other symptoms which turned out temporary. Could you please tell me why my thumb feels so weird when it’s stuck straight in one position (without any pain), just feels like I can’t control it? And I’d be very happy if you reassured me it’s not ALS because I’m so scared and obsessive about that. I’ve been taking antidepressants for some time, but they sometimes stop helping me.