How do you keep going and not lose hope?

Recently, after years of misdiagnosises and rejection of having a diagnose I got closest diagnose that desribes my illness(c-ptsd and bipolar). But the problem is that my mental state relapsed recently after 6 years of working on myself and medication. Psychiatrist said I was actually in subdepression all this time when I though I "achived happiness and stability". So in reality I don't even know what stability and happiness feels like and probably never will because when I'm ""grounded""(not escaping reality or dissosiating) I feel existential pain. Like the life itself is so cruel, meaningless and painful. They won't presccribe me antidepressants, only antipsychotics because I have also bipolar. And antidepressants for the last 4-6 years it was the only thing that gave me hope. I barely have any any hypomania episodes for the 4 years(I had bipolar symptoms for 2 years straight before, thats why they gave me this diagnosis). It's like having a chronic pain but then doctors said it will be forever and say that you don't need painkillers. How do you keep going if everything is meaningless and depressing? (If that's important, I'm 24 and had differend traumas since I was 5 untill 18)