is this the 18 month sleep regression?

my son has never been a great sleeper so im not super familiar with all the regressions. he did begin sleeping through the night the past couple months, and for the past week hes been waking 2-3 times. tonight and one other night this week he has woken totally inconsolable and hysterical. like wakes up screaming and will not relax. does not seem to matter what i do. the only thing that calms him down is bringing him to bed with me but all that does is wakes him up even more, and he wont stop moving and sitting up etc so i end up putting him back in his crib where he gets inconsolable again, and like i mean youd think he was dying or something. just screams. after nearly 2.5 hrs hes finally asleep and i ended up just letting him cry it out because i didnt know what to do. im 33 weeks pregnant and so tired and get irritable too fast for my liking... tell me this is a phase that will be over before i know it.