Holy cow Man... Unless you tell me that you are a collector I'll say your problem is that you are using way too much equipment! HAHA.
The properties and acoustics of sound will produce some of the "back pressure" or resistance that you feel. It is ok. If there were no resistance, we would not be able to play for longer than it takes us to exhale without the horn. The "trick" is in learning how to control your breath in a manner that doesn't cause you discomfort and also is highly efficient... which leads us back to the yoga, swimming, etc. Try it for a few weeks, see what happens.