Sleep problems! Advice!

So my little guy is going to be 14 weeks tomorrow. Recently we transitioned him from the bassinet portion of his pack and play to the big part of it to sleep. He seemed fine for the first few nights but for the last week every time I put him down in it he cries or he’ll stay sleeping for a half hour tops and cries. He went from waking up twice a night to waking up like every half hour or so unless he is sleeping with me. Anyone else be this struggle? What did you do?