Wow, most boxers I know have confidence for days. Did you lose most of your amateur fights?
I think I had this same disorder for a while during my teen years. What really helped build back my confidence was lifting weights, once I started getting results and looking better, I got back the bounce in my step. I went from being tense and nervous around people(especially females) to being calm, cool and collected.
Just focus on bettering yourself. Stay in the gym, keep yourself well groomed, stand up for what you believe in and get some IT certs.