Hello Mummy! Sorry to hear your baby has been in discomfort recently. It's really confusing to know whenever they cry and we don't know why. The culprit may be his teething. Have you tried giving him a teether to soothe the pain? This article might also help: https://sg.theasianparent.com/treatment-for-babys-teething-pain/?utm_source=search&utm_medium=app
Have you tried teething gel? And sleeping earlier as it could also be due to overtired.