I'm going through something similar at a much smaller scale (startup CTO of 2 years, not much growth). It's been enough to make me want to quit software engine

I'm going through something similar at a much smaller scale (startup CTO of 2 years, not much growth). It's been enough to make me want to quit software engineering altogether. It sucks. At least your company is growing and you know that you are a decent developer. Maybe you can take a sabbatical. Talk to your partner if you are on good terms. Make sure to explore your options. Hope you find a way to move forward and regain your confidence.