You know, you said you spent a lot of time around people. While that can be draining for us introverts, it can also lead to a "let-down" period afterward. Two weeks ago, I had depression come out of the blue. I still don't know what caused it.
You said you don't have many "skills" to help you cope with this stuff. Has your T ever tried to teach you any coping skills?
If anything, know you aren't invisible. You are getting plenty of replies to your post here. We see you!!