Oof, knee pain after 5 months postpartum ay common talaga especially kung kano-carry mo ang baby all day or sleep-deprived ka pa! Sa akin kaya ng knee pain was from always sitting sa weird positions while playing with my kids, plus ang bigat ng baby carrying eventually takes a toll. Try rest muna, ice packs, and maybe some paracetamol, pero if it's getting worse or hindi bumababa after a few days, best to check with your doctor na para ma-rule out kung may inflammation or something else going on, 3 days pa lang pero better safe than sorry lalo na kailangan mo ng energy para sa baby mo!