3 month old crying except when at breast

My baby has been crying nonstop unless I breast feed. If I breastfeed he kmmeadiately stops crying. The second I put him down from breastfeeding he cries more. He's only content When he sleeps at night or feeds. He never used to do this. I thought it was a growth spurt but it's been going on 2 weeks. I ebf and never had this problem until recently. I don't understand what's going on! Help!