7 months baby cryes at night

You - posted 8 minutes ago 10 Hi I have 7 months old baby. Until 3 months he slept so good he didnt woke up at nights at all. He didnt want even to eat. But from 3 months till now every night he starts crying every 30 mins- 1 hour. He sleep all night from 9 pm - 8 am, he dont woke up but he starts crying and only thing what helps is a bottle with milk. He dont eat it all. He eats a lil bit and then hes good for another 30 min - 1 hour... I dont know what to do...that he would not cry at nights..Does anyone had problem like this?