Is it normal to feel extremely weak and tired 5 days post-op rhinoplasty?

Almost certainly not. You can not really see anything through the dressing, the splint and dressing will change the way it looks and there is a lot of swelling. In fact it will be many months before the true result is visible. I hope this helps. 

After reviewing your photos, your nose can be very challenging as you have very thick nasal skin.  I always give my patients relatable analogies:1. The thickness of nasal skin is extremely important to the outcome of a rhinoplasty.  Imagine throwing a silk sheet over a chair....

At three weeks post procedure it is relatively easy for trauma to the nose to cause injury that may affect your final outcome. The nasal bones are only partially healed at this stage. Particularly if you heard a 'crack', then you should definitely be reviewed by your surgeon to see if anything...

You may certainly see a difference, however, this is to be expected after surgery.  In my experience, it can take from 6-12 months to completely heal after a surgical procedure.  Be patient and keep in touch with your surgeon to discuss any future concerns.

As a rule the nasal bones have become very well stabilized by 8 weeks following surgery via a fibrous union. A minor trauma at 10 weeks is unlikely to cause any changes to the bones and no more likely to cause problems with the cartilages than such a trauma would have done before your operation...

No.  It is not reasonable to have any "elective" surgery during pregnancy.  The medications and anesthetics required could affect the fetus and the stress of healing would add to the demands already placed on your body with the pregnancy.