Yes i do regret not believing in bitcoin but you can not change that anymore you can join the bitcoin community and start right now but i would still regret the fact that i did not join earlier and invest in bitcoin when it was very cheap.
I also feel this way during I'm newbie. Because the price of bitcoin by the time I start using it was around 400$ each only. And when I research it's price history. It's original price was 1$ . But I believe that bitcoin will still pump I decided to start earning and hold it. And now look what is the price. The moral lesson here is never stop believing on BTC.