Rough night ahead

My poor little angel has been miserable all day and has been waking up every 30 minutes since I put her down at 10pm. It's currently 12:49am and I'm rocking her back to sleep. I know something is wrong by how she's crying, but I just don't know what and it's killing me. I just gave her some Tylenol and that seemed to relax her. She's 3 months old, 14 weeks and 2 days. Any ideas on what it could be? She's never been a baby to cry hysterically without reason...😔 I wish she could just tell me.