Trouble breathing,and feel fatigued?

lately i thought it was anxiety, but i cant breath throughout the day its on and off, usually sleep helps. my doctor says its anxiety and my sleep cycle is worsening it because i stay up till 3 am . but i dont think this is the case randomly ill just have trouble breathing and it has like a burning feeling in my lungs, also sometimes it feels like my chest is congested, but i have no cold, and have never smoked,but have been around smokers my whole life. Also i feel fatigued. When i wake up i try to go get food but and so fatigued and out of breath i have to sit down. A couple of weeks ago i was exercising and feeling great than this came out of no where. What is this please help i have no energy i just lost weight im going to gain it back i feel terrible.