Am I Underweight 5'9 124lbs?

Hi I been sick with the flu finally getting better and am eating now. I am a White Male 35 years old 5"9 124 lbs. Am I to thin or underweight. Because I lost over 25 lbs while I was sick. Before I got sick I was about 148. Today I weighted myself and I am 124 lbs. Am I to thin or what? I am nervous because I am still Loosing weight about a pound every day or so. Respond thanks. I need to gain it back quickly and I need help because I am still loosing weight. How can I stop my body from loosing and start to gain it back. Respond thanks