Depressed once I adjust to situations

I have high functioning anxiety and on and off (high functioning) depressive episodes. I am seeing a therapist every 2 weeks mainly for my social anxiety. But I was wondering if anyone relates to the following and maybe has some answers for me? (I don't see my therapist for another week and am a little desperate).

1st year in secondary school (11th grade): I was motivated and excited and I loved it. 2nd year I start to get depressed and anxious, barely make it through 3rd year. I graduate (barely), feel good and start working full time.

I get a job at a preschool because I like kids. End up liking the job. 4 months in and well adjusted, I start to get tired and depressed. I end up working there for 2 years depressed af.

I sign up for university and quit my job. Feel great, all problems gone. I take a 4 week summer art course before school starts. I love it, can see a possible future pursuing art? 3rd week in, I get tired and it gets hard to show up. Rest of summer I just chill and feel bored but fine.

University starts and I absolutely love it, find it so exciting, find love in studying. 3rd week (last week), I cannot show up to class because of mental fatigue and anxiety (not even to online classes). It's now the 4th week, trying to push myself to go to class (at least the online ones). This morning I managed it but 30 min in I got so tired, all I wanted was to log off. 30 mins ago I had another online class but every time I tried to log myself onto zoom I would burst into tears.

Why do I get like this everytime I adjust to new situations? Shouldn't it be the other way around? I get so tired, mainly mentally. I lose all motivation, interest and excitement. I barely trust myself when I try to plan my future because of this happening. I'm not the type to quit and just give up once things get hard, I just don't know why this always happens to me. I'm getting tired of being tired all the time. I know the fatigue is mental, I eat healthy and exercise regularly, but even that is getting harder to do now. It makes me scared to do things that excite me in fear of them becoming a trigger to my depression soon after I start. I burnout over the slightest pressure. I just don't know what to do...