If he is regurgitating, it might be too many mice or too big of an item or the cage is too cold. I've feed my 8 week old baby BP a 28 gram rat and she weighed 138 grams at the time. It looked like she ate a football and she pretty much went into a food coma on the spot and slowly slithered into her warm hide. She got it down and didn't regurgitate luckily but regurgitating for a snake is a very uncomfortable ordeal so I would wait a week before you feed again so the snake has time to replenish his stomach acids.

You're better off starting with a smaller meal and watching how he acts, does he go into hunt mode in 2 days or 1 week etc. Then you can adjust the size based on that as snakes tend to not like to expend energy unless needed so if he is out hunting and looking for food at night, it probably means hes hungry