Hello Bretange,
I was so sorry to hear of your recent health problems. Many healthy people experience muscle twitching, and these are not usually a cause for concern. Often this symptom can be caused by or exacerbated by stress, lack of sleep and caffeine consumption. With regards to the pain and weakness in your bicep you experienced after prolonged clapping or when carry things, - again this is not something that we would associate with an MND diagnosis.
I do hope that your GP is being supportive of you and that you are seeking help for your health anxieties.