For blocked nostrils, there are several nasal drops available in the market. You should consult your doctor about your problem before using any home remedy or medicine. As you said, it's easy for you to sleep straight and turning causes a problem, it may indicate that the air pressure changes with your position (you've stated that you live in different environments). Try to use two pillows, they shouldn't be hard, while sleeping. Sleep in 45' angle and don't completely take a turn. Apart from vicks inhaler, if you simply rub some vicks balm under your nose, that'll give you big relief. Use saline drops and herbs in steam inhalation. There's a technique to unblock the nostrils, a very common homely technique it is. Just press your nose and don't breathe from mouth as well. Sit silently and keep pressing your nose. Once you start feeling an urge to breathe, release your nose and breathe deeply. This will clear up your nostrils.
Go for some medical treatment. Above tips are additional. If you feel mucous in your nose, pouring a drop of lukewarm mustard oil in the nostril may also help you. (Make sure the oil is not much hot, put the oil on your hand and if the temperature is perfect, then only put it inside your nose, it should be a little warm though). Do some yoga, such as anulom-vilom, for natural benefit.