Brain over load

Well I`m back in hospital for a cocktail of iv`s so two weeks of  nausea. Lung function and exercise tolerance down but on a positive note  I can say I don`t feel all that bad considering the year I have had.
When you feel as though each day is a challenge and feel ill  90% of the time I think you adapt and it then becomes difficult to judge when you need iv`s.  I have only been in 4 days but all ready I can feel the difference apart from the nausea.
Something has been really puzzling me at the moment, my lung function is low which I except but what I can`t get my head around is after all these years with mostly the same lung function, I have managed to get out and about but now I need oxygen when walking even the slightest distance. WHY when my lung function is more or less the same??? I have always struggled walking up a flight of stairs or walking my dog but not to this extent, I hate it when I am so out of breath and have began to slightly panic.
I am trying to use the oxygen when walking the dog etc but am finding it difficult to be out with it even though it really helps. I have given it much thought as to why the obvious one is people seeing me but more so family which is silly I don`t want to be seen as the helpless one I guess, I am a young woman yet can`t do the thing in life I have so very much wanted, not going to university has to be the most upsetting and  going on holiday with friend abroad would be nice. The biggest reason I fear if I start using oxygen is this how it is going to be from now on ? I am trying to fight back but am I just fighting a losing battle to go without? I see the oxygen as this is how its going to be from now on and it scares me to think of it like this, my lung function is very very unlikely to dramatically improve I don`t have a back up plan that option is out for me.
I am finding putting thought and feeling in writing helps .
On a happier note my nephew got married last week and his wife is so nice. The party was in a hall with puddings family made and my brother in law did a barbecue everyone had a good time.