There is no direct relation with asthma and Fenolip or even erection difficulties. You should get your fasting sugar HbA1c to rule out diabetes. Erection difficulties could be due to several reasons and if you do have diabetes you should get your TSH, free testosterone (8 to 9 am) and Prolactin done and meet an endocrinologist. Abnormal lipids level can lead to erection difficulties and this can lead to what we call vascular disease. Erection requires your vessels to be filled with blood.