Nutrition, asthma and sex

Patient: Hello Sir, am single guy age 39, recently i have noticed that i feel fatigued after evening and just feel like sleeping all the time.. also my sexual performance is bad… i get erection pretty quick but after first session i dont get erection for round 2.. even the first session is for 15-20 secs… is it coz of lack of oxygen in my body.? as am asthamatic.. although am taking medication currently for the same and the results are pretty good.. i havent used my pump or nebulizer since i have started this medication around a year back.. kindly advice..

Symptoms: Feel tired & fatigued by evening, feel sleepy and weak all day, lack of strength, erection is hard but intercourse doesnt last more than 20 secs.. and almost have to wait for 2-3 hours for round 2.. sometimes even that doesnt happen

Doctor: