Breathlessness

[Jame12]

Hi,
I am 25 year old and for the last year i have been experiencing breathing problems, it feels as though i cant get a full breath of air into my lungs, it is very uncomfortable and makes me yawn alot trying to get oxygen in, i will often also experience tightness and pains accross my chest at the same time and it seems once it starts in the morning i cant get rid of it for the day until i go to sleep at night. I have been to the doctor several times and they have tested me for asthma, which i dont have. One doctor suggested it may be to do with Anxiety and prescribed me antidepressants of which i havent taken as i dont like the idea of taking them. I have tried breathing exercises which help briefly but wont cure the problem. I suspect it could be something to do with milk, i have always been a big drinker of milk throughout my whole life but it has never affected me until now. I have done expreiments and tried not drinking milk for a few days and it definately stops the breathing problem then if i drink milk again i seem to expierience the problem again, however not always. What i dont understand is if i am reacting to the milk why can i eat butter, cheese and cream without it affecting me?? Do you think i am correct in thinking that i have an allergic reaction to milk? And if so why only within the last year have i experienced the problem when i have drunk milk my entire life?? Please help