Sleep Training

I am currently sleep training and it’s probably the hardest thing I’ve had to do ever .. 😭 it’s been 45 minutes and he’s still crying ! I’ve been going in every 10 to 15 minutes .. my firstborn slept through the night at just 3 months this baby is just 4 days shy of 6 months .. idk what else to do ! 😭 I know he doesn’t need more food so I shouldn’t feed but he doesn’t stop crying ! 😭 it’s routine that he wakes up at 3am . I guess I just need some reassurance. 😩😩