Your sinuses are suffering from vasodilatation or nasal congestion. There's nothing to blow out that will unblock them because the passages themselves are shrinking due to the blood vessels increasing in size, and the nasal passages shrinking as a result.
Normally your sinuses do this throughout the day following a nasal cycle that allows one side to rest and remoisten while the other side handles the majority of the airflow. The frequency of this cycle depends on the environmental factors.
But now your body is fighting an infection and it's decided to play Madagascar and shut down everything. Both nostrils are not only congested, but severely so, to the point where you can't use them.
Some of the treatments suggested do provide some relief. Sitting up decreases blood pressure in the head, decreasing vasodilation. Hot steam provides very temporary relief. A nasal strip can pull the nasal passages open a little more widely. If your congestion isn't severe, or if you fall asleep quickly, then these might be sufficient.
It sounds like your congestion is bad enough, though, that you should look at vasoconstricting medications, otherwise known as decongestants. I recognize you've tried some decongestants, but there're two things you need to understand - first, one very common, over the counter decongestant in the US may not be effective, and second, a nasal spray decongestant should be tried if you've only taken oral decongestants so far.
Typically nasal decongestants will work in most cases. Pseudoephedrine is the most common over the counter oral decongestant that people indicate works, though in the US it is controlled so you'll have to ask your pharmacist for it (no prescription required). Note that if you're buying an over-the-counter decongestant in the US that doesn't require you to visit the pharmacist, it's probably Phenylephrine, and "clinical studies suggest that phenylephrine is ... not more effective than placebo". Make sure you try Pseudoephedrine before you give up on oral decongestants. Check your medicine ingredients, and talk to your pharmacist if you have any questions.
When that doesn't work, however, I've found that a direct decongestant spray, oxymetazoline, works very quickly and effectively. This is common enough that you can find it in many brand names and generics, such as Afrin. There are a number of nasal sprays that claim decongesting effects, but some are simply saline spray. Make sure you try one with oxymetazoline.
They all work the same way but use different routes to the affected area. Direct nasal spray application works very quickly, but can't be timed release, so may need to be used more frequently than an oral decongestant. Further, they are different drugs, so if one doesn't work, it's worth trying another to see how your body reacts. For me, oxymetazoline beats Pseudoephedrine which beats phenylephrine.
There is an issue where if you consistently use them your body starts to work harder to close your nasal passages, which means that once you stop you become congested even if you would normally not be congested at that point. As such, I've limited my use to only when I need to get to sleep, and usually only one spray (1/2 to 1/3 the recommended dose) in one nostril (I don't need both open to sleep), and alternate nostrils each night. Usually, I've only needed it for a day or two. If it appears you need it for more than a few days in a row, you should probably consult your doctor or GP to check for bacterial infection or other causes, or a plan to wean you from the medication once the cause is resolved.