Daycare suggestions

So my son (only child) has been going to daycare for about 2 months now. He was 5 months when we started. Ever since the beginning he has been having a hard time adjusting to it. He would always want the attention or throw his head back when he cries. So I told the teacher to maybe try giving baby food and I had also sleep train him, hoping it'll help. He also started crawling a couple weeks ago. They kept sending us updated pictures and he looked so happy and energetic. So I thought everything was finally going well. Well this morning the director told me when I dropped him off that he was still having a hard time with daycare and now they are starting to have more babies coming in so it's not as easy to do one on one with him. Do you guys have any suggestions for me to help make it easier for him when he's at daycare?