Vitamin D deficiency: anyone had this?

I have had bad health issues for years. I would every once in a while tell my GP who then said it was all in my head, it was stress, it was the traumas. I told them I didn't go outside and didn't live and eat healthily, but nothing was done, they have a 'next' mentality so I recently switched GP. He immediately sent me to the lab for bloodwork. Not only that: the results came in not even two hours later!

I was diagnosed with major vitamin D deficiency. There are weird and very off values concerning muscle and mass as well, which only proves what I wrote about a while ago: I have lost so much muscle due to depression and only sitting on the sofa with the laptop for work. I haven't been outside in years, living an online life that was a bit easier to manage, avoiding extra stimuli that would create flare-ups of the traumas I worked on during therapy (which is still ongoing).

My major concern is: can the damage of this deficiency be reversed? I have had so many complaints about my health for YEARS that now seem to come together. I was so depressed for so long, have tingles and strange sensations all over my body especially in my legs, I can't concentrate and focus, am very forgetful, have headaches, high blood pressure and my heart doesn't even react well to the medication anymore. I am, all things considered, quite the mess.

Does anyone here have any experience with this?
I hardly go outside, I know I should get some sun, but this is not yet possible for me (too stressed, too much happened). I am a mess! I used to be outgoing and moderately active a few years ago but something bad happened and I'm working through it with help, until that time I won't go outside, but I think I may be getting there.