So I used to be in a very similar boat as you: I was depressed while working towards a STEM degree in college and ended up almost failing out with a 2.X GPA. I didn't see a path forward, and there was only one entity that was willing to hire me to do "real" work (for basically minimum wage). Like you, I thought I was totally fucked. Turns out, I wasn't. I spent the next 7 years working incredibly hard at that job. I taught myself software development skills in a similar manner as you out of personal interest. Eventually I was skilled enough to make major contributions at work and transitioned into a developer role. I continued studying and also took some remedial courses at a local university to prove that I could get A's if I tried. I then applied to a Master's program with glowing recommendations from my employer, a proven professional track record of success, and the transcripts from the local university. I was sure the admissions people would laugh and toss my application right into the trash. Guess what? I got into a great program! I'm now working in my dream role at a tech company, I got the opportunity to go back and prove to myself that I could succeed academically, and I learned a lot while in the program. You are already at a prestigious company as a full stack dev, so your road could be A LOT shorter than mine. I will give you the following advice based on my experience:

1. Realistically you are doing well. You are already in a great role; it sounds like you may just be struggling a bit. You mentioned feeling overwhelmed: have you reached out to your manager or a more senior engineer on your team for help? I bet they would be able to identify any weak points that you have which you could fix with self-directed learning (which it sounds like you are experienced at). Has anyone made a comment on your performance? If not, is it possible that some of your feelings are driven by imposter syndrome? The fact that you were hired despite your academic record suggests that you are certainly a competent dev.

2. No one likes hearing this, but you need to be patient. You only recently began your professional career (whereas I am in my mid 30s), and it will take time to build up the reputation and the track record to offset your past. By "time" I mean probably a few years minimum. Don't be deterred by this though, as these few years will be periods of heavy growth. I should also note that when I say it will take time to offset past performance, I am speaking purely from an academic perspective. From a professional perspective, you left your academic record behind when you got your first job, so I wouldn't spend time dwelling on it.

3. I agree that getting a Master's degree may be helpful, if for no other reason than it sounds like you may have a chip on your shoulder about your academic record. If you are serious about going back to school, take the following actions:

* Work. Fucking. Hard. Build a track record of success in your role.

* Get a portfolio of projects together that you can show off.

* Continue your self-directed learning and fill in gaps in understanding yourself. Work with your manager / seniors to identify these.

* Succeed in some sort of graded endeavor that you can use to display that you are serious and diligent: take courses somewhere and get A's; take coursework on Coursera or something else and get a certificate; get an industry certification or two; do research and put out a paper; etc. Basically you want to show the program that you can succeed academically and that you won't flake out if they admit you.

If you want to chat about your situation further, I'm happy to do so out of band.