My 12 week old son was drinking well from his bottle on #2 teats but fusses and spits it out and cries now. I moved him up to #3s but he often chokes and needs to stop often as if to catch his breath. He's still eating well, gaining weight and getting enough milk but every mealtime is a real struggle now. He isn't colicky and brings up plenty of wind on his own. Is this just a normal phase??