Hello, welcome to health care magic. I am Dr Alok Sinha, MD Psychiatry from India. I will try my best to answer your query. Erection of penis has many components. Due to sexual arousal some of our brain cells get activated and send signal to genital organ via spinal cord. Penis has erectile tissue which respond to these signals and gets erected. As you told you are young male, 28 years old and having good sexual life in recent past, so there is unlikely any structural deficit. It appears that it is anxiety/ depression that is causing problem. Vascular problem or neuronal problems at this age is unlikely. Depression/anxiety put mental stress. Any kind of stress causes increased cortisol and steroid level in body and stimulates sympathetic system of body which in turn works against erection. Secondly you told that you are overweight. Obese persons, due to upper hand of female gonadal hormone in body may experience low desire for sex, not the erectile failure. it is good that you started working out now a days. If a person like you comes to me I evaluate them first in detail for anxiety and depressive symptoms and treat accordingly. Viagra like medicines act locally at genital organ to increase the blood flow when signal comes from an aroused brain. In your case, the cause is not at lower level, rather it is much above in brain. I suggest you to get professional help of a psychiatrist. You may get benefit within a week or two. All the best.