Hi and welcome,
I wouldn't be thinking it could be something like a neurological condition like MS, you said this only started in the last few days "feel numbness in my hands, feet and sitting place (not consistent) and extreme tiredness in my legs. But these symptoms also keep changing." ....it is very inconsistent for MS to present in all peripheral limbs (both hands both feet), MS symptoms are caused by brain and or spinal cord lesions, so MS basically doesn't cause symptoms to move around the body, change depending on body position, spread etc.
I don't quite understand what you mean by "While I am sitting I feel my head is shaking (slowly)" and when you say 'most obvious' do you mean to you or other people? Sorry, all i can think of is the slow head movement of up and down (vertical or nodding yes), normal because it's due to the slow minor physical movement of breathing.
I have a head tremor (horizontal no no) but i wouldn't be able to describe it as 'slow' or even fast, it's a consistent rhythm of left and right that never stops so i'm finding hard to imagine what you could be meaning, again sorry.
Stomach bloating is not an issue associated with MS, if the urologist didn't find anything abnormal to explain the frequent urination and recommended behavioral changes, it's highly unlikely it was consistent with neurogenic bladder.
Off the top of my head the only things that comes to mind are structural spinal issues eg degenerative disc disease, sciatica, compression etc or viral infections, vitamin deficientcy but it honestly doesn't sound like MS to me...
Hope that helps.........JJ