Ebf 4 month old waking every 2 hours!

My 4 month old finally started to go to sleep at a reasonable time, around 7.30pm. He used to not settle till 12pm. He stared sleeping between 5-6 hours then wake for a feed then sleep another 2-3 feed then another 2. The past 2 weeks he is waking every 2 hours for a feed and it's killing me. Sometimes he can feed for a good 45 mins at a time. I'm ebf and considering giving him a bottle of formula before bed in the hope he will sleep longer. Is anyone else going through this sleepless nightmare while breastfeeding?