Brief Answer:
No MS

Detailed Answer:
I read your question carefully an I understand your concern.

Regarding the fear MS I would go ahead and say that it is not the case. Your symptoms are not typical for MS at all, most of them do not have any anatomical relation to any brain or spinal cord involvement. If that wasn't enough there is also the normal MRI which would show some lesions in over 90% of cases, so combined with atypical symptoms I would take that to a 100% certainty of not being due to MS.

As for other connective tissue autoimmune disease like lupus...they can have many different manifestations involving different body systems, so to exclude them with certainty is difficult. I can say that you do not fulfill the criteria for lupus. Do not have any specific indication for any other autoimmune rheumatological condition either.
However these conditions do not have only clinical criteria but also laboratory ones. So given the fever and the murmur you've been told to have you should go through with the heart tests you've had as well as blood tests for inflammation markers (ESR, CRP, fibrinogen), hematological changes (full blood count) and common antibodies found in autoimmune disease like antinuclear antibodies, rheumatoid factor etc.
If at the end nothing abnormal comes out (fever may be due to simply a passing infection) and your physician finds nothing else on physical exam then I would consider anxiety as a possible contributing factor at least partially. It can also be associated with chronic fatigue sindrome which would justify your exhaustion.

I remain at your disposal for other questions.

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