How can I say that you are a pro gambler? You are stating by yourself on this:
For a couple of years, I had a lot of success betting on football from very obscure leagues. I had an algorithm which was great at spotting games where bookmakers had not priced up correctly.
What? I don't see any thing on that quote which supports your statement. OP mentioned that he became successful on sports betting and not on poker. Nah, nevermind.
Anyway, IMO it doesn't mean that you are already considered a pro player just because you have many years of experience. That's not the only qualification. It also depends on how good your skills are, your win rate and how big the assets (money and possessions) you earned through this game.