Feeling disconnected from the world

Does anyone else go through this feeling of just wanting to be alone and isolated from everyone and everything? This all happened almost a month ago where I suddenly fell very ill for 2 weeks. I went to the ER twice, and all lab work, tests, and examinations came back negative. In fact, they all said I was in "perfect health". When this started, I didn't eat or sleep for almost 3 days. I had chest pain, shortness of breath, no appetite, to name a few of the major symptoms. I'm able to eat and sleep again like normal but, I've never been able to fully recover from whatever it was I went through. My body always feels weak, I have low energy and, mentally, I don't seem to have the motivation to care about anything, work related or otherwise. I've never been depressed before but somehow I think I am atm. I've always been a nostalgic person, reminiscing on the past, but that only seems to fuel my sadness these days. I don't take any medications. My diet has mostly been the same throughout the years. I don't know what happened or is happening to me. Alhamdulillah, despite having missed some fasts during that time, I'm still able to full fill my basic religious obligations and inshaAllah I will be able to make up the days missed. Has anyone gone through, or is currently going through such a thing? I don't know what to do or how to cope with this.