My DS is 10 weeks. He's always been on size 1 teats (mainly MAM, some Lansinoh bottles). I noticed the other day that size 2 is recommended from 2 months so duly bought replacement size 2 teats for his 6 MAM bottles. He doesn't seem to like them very much, is spluttering, whinging and leaking a bit. Should I just switch back to size 1 or persevere? What happens if he stays on size 1? Does he just need to get used to size 2?