Potty training regression!!!!

Casey
Anyone have any advice on this! Our son is 3.5 and has been diaper free (except for poop) since 3rd birthday. He's always done great, we never pressured him, and made training very easy. Lately within the past 3 weeks he's been peeing his pants sooooooo much. He used to just up and run to bathroom when he would feel like he had to go really bad, but now he doesn't even say I peed my pants I only know because I'll feel him or see it's wet. I'm so stressed and have no clue what to do, I don't want to just put him back in a diaper all the time.....any advice is appreciated.