underwater face-up with breath control

Hi all, First of all, if there's already a thread concerning this issue, I would like to say sorry for opening an already existing topic, but also would like to ask the moderators to link me the topic discussing this, before closing this thread. The thing I wanna learn is being face-up underwater without having water in my nose but also without releasing a bubble, using breath control. (not nose clips, not my lips, not anything else, I wanna do this with breath control) I have been practising this a lot now. Yet still can't manage to do it. All my acquaintances who ever tried or practiced it and can do it say that it is easy and they didn't need to practice it for too long. I can do it vertically, btw. So no, before you say, I am not instinctively sucking in water. What I start to think is that what prevents me from being able to do this is that I have adenoids. Most of the time I can barely breath through one of my nostrils, which makes an unbalance between the 2 nostrils and makes it impossible to even the pressure at the same time in both of them, resulting in flooding my nose in any way. I also realized that I can either blow very little bubbles, or stop my breathing out completely, but between the two, to apply a pressure which is enough to keep water out but not enough to release a bubble, is just impossible for me. There is a gap in the breathing out I cannot acquire. Even if I do, one of my nose gets flooded because of the give unevenity. What makes me very sad is that all of my acquaintances who ever tried or practised this, could master it easily. I have been suffering with it now for so long. But my fear is that with adenoid I won't be able to master this. Anyone any experiences on this one? Any tips, suggestions on how to practice? Thanks