Are both nostrils supposed to be open? only one side of my nose is open at a time never both.. why? what can i do its really frustrating

Mostly, yes: Generally, you should be able to breathe from both sides of your nose. There is, however, a natural cycle which shifts relative congestion from one side to the other. If you have a blockage like polyps, a septal deviation or weakness of the structure of the nostril, one side actually may be way more difficult to breathe through. Try to see a Rhinologist or Facial Plastic Surgeon; both are ENTs.