Never regret love. It is a treasure in the memory, long after the loved one has vanished.
Having said that, I think the prognosis for your triad is good, and that the three of you will probably stay together. It's important to remember that relationships -- especially poly relationships -- tend to be quite a roller-coaster ride in the early years. The highs are great, but the lows really suck. You have to have patience and faith, always practicing improved communication, looking forward to the time where things will level out (on a high, comfortably ascending level), and the turbulence of the past will become a harmless memory.
You have the right idea. Bask in the goodness of this moment, here and now. We can never go back to the past, we can just be glad that we appreciated the good things that were there.
I am pulling for you and wishing you the best.
Love means never having to say, "Put down that meat cleaver!"