Sleep after starting solids

My boy is 6 And a half months old and used to sleep 7.30pm till 7.30am only waking up if he needed the dummy back once or twice and went straight back to sleep. Since I've introduced solids he's been waking up multiple times in the night and taking ages to go back to sleep. Also wakes up at 4 for a bottle and bsck to sleep till 6am and then he is ready to get up. what is causing this and how can I stop it and make him sleep again?