A- Easy fatiguability (that is, the fact that you have poor exercise tolerance manifested in fatigue after climbing up a few stairs) and shortness of breath after showering (in hot water I presume) is most likely a result of:
1. Anemia (due to iron deficiency, heavy menstruation, or both, or thalassemia trait which is very common in the Middle East area; you need to check if there's family history of this illness, it's not dangerous but you need to be aware as). Anemia means your red blood cells cannot carry enough oxygen, therefore prompting your heart to pump more blood to meet the demands of your body organs
2. Thyroid disease: a lazy thyroid gland produces symptoms of lassitude, in addition to things like unexplained weight gain, constipation, dry skin ...
B- Nasal septal deviation: the surgery you underwent is called septoplasty, and a known complication of it is Nasal obstruction due to failure to straighten the septum or later re-deviation of the septum, or the re-growth or swelling of the turbinates (these are tissues found in the nose that provide humidity but may sometime enlarge and block your nose). When your nose is blocked, you breath through your mouth and end up having what we call obstructive sleep apnea (OSA), and you get unexplained daytime sleepiness (This is the major manifestation), restless sleep, and loud snoring (with periods of silence followed by gasps). Less common symptoms are morning headaches; insomnia; trouble concentrating; mood changes, forgetfulness...It is imperative that you reconsult your ENT Dr as your condition may necessitate revision surgery.