cosleeping during sleep regression

my baby (15 weeks) has been sleeping in his own room great since 6 weeks but is now going through a sleep regression and isn't able to sleep alone whatsoever. i put him down and immediately he wakes up and will not stay asleep unless im holding him. i've been cosleeping with him this week bc it's the only thing that will let him sleep, when will this get better?? will cosleeping make him unable to sleep alone again?