As a fellow BFA-haver, I also get that sinking feeling sometimes. I've been at my first real dev job after a boot camp for about a year and a half now, and my first tech lead/crazy awesome mentor left the company recently. He had my back through a lot of tough challenges while pushing me beyond my comfort zone, and when he left, I had the sudden thought - "Now that he's gone, everyone's going to see how much I suck." I immediately laughed at it because it was so stereotypically imposter syndrome, but at the same time... I still felt it.
A few months on, and I'm still doing well and competent and not fired and all that jazz, but there's a crazy dichotomy between knowing that I add a ton of value at work, and feeling like I'm worthless/a fake.