Depression and PVF are completely different, as you'll know. I can see how the presentation can be confused but there are clear differences. So try not to let them convince you that anti depressants are going to make you better.
By way of explanation, my DD(18) has had ME from age 14. She had glandular fever and didn't recover from it. There are a number of underlying causes to ME but hers is most likely post viral.
She did the 2-day CPET I mentioned and it showed that after (deliberately) depleting her energy envelope and continuing to exercise, the following day she had 42% less energy. This result is unique to ME and proves her metabolic energy system is faulty. It shows why pushing on and ignoring it is just going to make her worse.
By resting and understanding what's wrong with her, she's improved from not being able to get out of bed 4 years ago, to reliably leaving the house for an hour or so three times a week. It sounds like your function is a lot better than that now, especially if you got better for a while, so hopefully just understanding what's wrong and with the right approach, you have a high rate of recovery.
Depression, as well as PVF, is a possibility. But if you respect what your body is telling you and focus on the fact that you're rehabilitating yourself, it should hopefully give you hope that you'll be fully better again one day. And that it's a means to end rather than a new lifestyle.
The hardest part is dealing with people's attitudes tbh, but I found the exercise test results shut people up when they try to suggest DD is just trying to get out of going to school.
So another good reason to try and get that done, if you can.