To stop checking for symptoms - if you are still not convinced that you do not have any illnesses including msa etc - then what you need is treatment for the health anxiety and fear of serious illnesses. I will try to provide you below with a list of various treatments that can help you in diluting this type of extreme levels of health anxiety and fear of serious illnesses that are unfounded.
The following is a list of various treatments that can help you in resolving this kind of severe health anxiety, fear of serious illnesses, stress etc;
CBT (Cognitive Behavioral therapy)
ACT (Acceptance & Commitment Therapy)
Other types of meditations
Deep breathing/Deep relaxation techniques
One or more of the over the counter Herbal or Supplement preparations like – Theanine (L Theanine), Rhodiola rosea, Valerian root extract, Ashwagandha, Ginseng-preparation (preferably American Ginseng), Chamomile, Inositol, Kava, L Tryptophan or 5 HTP (5 Hydroxy Tryptophan), Skullcap, Magnesium preparation, St Jones Wort, SAMe (S adenosyl methionine), Omega 3 Fatty acids (DHA & EPA) etc
One of the over the counter combination preparations – that contain a combination of certain herbal supplements + vitamins + minerals like magnesium etc - and examples for such combination pills include - Himazol Fast Acting “Extra Strong” Anxiety & Stress Relief Herbal Supplement, Stress Relief & Natural Anti Anxiety supplement, CALM NOW Anxiety & stress Relief Supplement, , herbal Blend, Genexa Stress & Anxiety Relief, CALM-ER Anxiety Relief Supplement, SERENITY RX- Anxiety & Stress Relief Formula, Alprazium combination pill (all Natural Stress Relief & Anti-Anxiety Supplement) etc
One of the benzodiazepine agents like Alprazolam or Clonazepam (not recommended for long term use, also preferably used in small doses)
One of the GABA structural analogues like Gabapentin or Pregabalin
One of the SSRI agents like Fluoxetine or Sertraline
Azapirone agent Buspirone
One of the beta blockers like Propranolol or Atenolol
Amitriptyline + Chlordiazepoxide (Limbitrol or Limbitrol DS - not recommended for long term use, also preferably used in small doses)
Using a medical devices such as CES (Cranial Electrotherapy Stimulation) etc
The above list contains names of allopathic medications, non-allopathic herbal medications, as well as non-medication treatment options so that the treatment plan may be chosen depending upon the individual preferences. I am not telling all these above treatments are required in your case, but providing you with a list of varieties of treatment options that are available for your condition. If you see any of the above treatments you have already tried please disregard them and consider exploring the ones you have not already tried yet.
In addition to the above special treatments general measures like adequate daily exercises, especially aerobic exercises and healthy & balanced diet is recommended too since they also contribute the dilution of the anxiety, stress & fear feelings.
You may try one or more of the above therapeutic interventions and these can help you in getting rid of this pathological degree of health anxiety & fear of serious illnesses that do not exist at all in your case.