I am looking for some answers

I am looking for some answers.
I am a 25 year old man. I have very mild CAH (congenital adrenal hyperplasia), and I take 2.5 mg of prednisone daily. Last year, I was on an Isoniazid treatment of 9 months due to a positive skin ppd (tuberculosis).

For years I have been experiencing dizziness and faintness and drops in blood pressure, but recently, along with my usual dizziness and weakness I have been experiencing a heavyness in my arms and legs, a weakness I can't seem to explain. It is almost as if when I lay down or sit down, my legs feeled nailed to the bed or the floor. Its like I have to think about moving them, since they feel so heavy. I've recently also been having back pain. It started with my lower back and I though I was sleeping wrong, etc., but after almost a month, this pain has spread throughout my back. It almost feels like flu pain, when your muscles ache. I am starting to get a bit concerned because these episodes are becoming more frequent, usually they would be months apart, but last Tuesday I got this way and yesterday (almost a week later) I got it again. This last one has even lasted longer...I still feel a bit weak in my arms and legs.

My paternal grandfather had Multiple Sclerosis and I wondering it I could be developing this.

Please let me know if there are any suggestions as to what I should do.

thank you.