My DS, now 10 1/2 weeks is now exclusively form...

My DS, now 10 1/2 weeks is now exclusively formula fed. Problem is he is only drinking about 100 - 150ml of milk each feed. He wants a feed nearly every 2 - 3 hours during the day and sometimes at night!!! I am exhausted. Does anyone know how I can get him to take 200ml of formula and feed him less often. The clinic health nurse said to offer him water or a dummy in between feeds, but if I give him too much water, he wont take the milk. I am following the feed, play sleep routine (or trying to) but don't know how to pacify him when waiting longer for a bigger feed. All suggestions welcome, Thanks.