Refocusing on What Truly Matters, Insha'Allah

Assalamu alaikum. I'm a final-year medical student from India and lately I've been struggling to concentrate on my studies. Alhamdulillah I've always been serious about learning, but recently I study for a while and then a wave of loneliness hits me. I get so down that motivation just disappears and I can't bring myself to keep going. I'm practicing, I've never had a girlfriend. Sometimes I catch myself thinking maybe I should've had someone to talk to or study with, but then I remind myself to follow what Allah guides me to and not give in to the nafs. Still, that doesn't seem to fill the empty feeling in my heart. I know dhikr and turning to Allah are the real remedies, and I try, but the sadness keeps returning. I notice many around me are in relationships or have found spouses, and those who focus on religion and are unmarried sometimes don't seem attractive - myself included. I'm not trying to be offensive, that's just what I've observed and it adds to my frustration. I've started feeling hopeless, like choosing medicine was a mistake. I try to count my blessings and be grateful, but often end up hating myself. I've had dark thoughts, even suicidal ones, because I feel stuck and useless. I want things that seem out of reach, and I worry I'm wasting the opportunities I already have by not working hard. I really want to be a good Muslim, a good person, and a good doctor. My goals are sincere and largely for the sake of the ummah, but without effort I fear I'll be of no benefit to anyone, including myself. How can I realign my priorities to focus on what truly matters instead of longing for things that aren't attainable right now? I need practical advice I can use quickly - my final exams are coming up and I need to be in the right mental state as soon as possible. JazakAllah khair for any guidance.