i don't have a relaxer but maybe i can help. i had one a long time ago, and in college i primarily used heat on my hair, so i can relate to dry hair that breaks.
what one of the commenters said, i think the immediate cause of why your hair broke somewhat suddenly was because of you detangling your hair while dry, but the inherent issue to your problem is simply that your hair is unhealthy. Unhealthy hair is weak hair, and weak hair cannot stand up to manipulation. so even though normally your response (not combing it and trying to minimize handling by resorting to just flexirodding it) might have worked and done wonders on hair that was actually healthy, hypothetically, on your hair it wouldn't make a difference because, as you experienced, by the time you did get around to handling it it was not strong enough to bear the dry combing.
my suggestion is that if you stylist didn't already trim your hair, go for a trim or do it yourself, using a good set of hair cutting shears. cut off to right above where the damage is, or according to about the length estimate of the broken hairs you normally see. broken hairs, if you amount enough of them in a relatively short amount of time, can negate length manifestation if your hair breaks off at a faster rate than it grows from your scalp. hence your hair appearing shorter, rather than merely staying the same length. neither is a favorable outcome, and must be managed via appropriate hair combing techniques.
you can't reverse the damage but you can lessen some of the effects by cutting off as much of it as you can and starting over with sounder hair care. since you're relaxed, this will include utilizing a protein treatment (such as aphogee) as often as the directions indicate. it's been a long time since i used aphogee, so i don't remember the specifics, but aphogee is a protein treatment designed for badly damaged hair. which if your hair has broken to the degree to which you've described, your hair qualifies for the treatment.
if you feel uncomfortable doing it yourself, then your stylist should know what it is or be able to recommend a similar treatment. i'm surprised she didn't mention it already, given the state of your hair.
the next thing to do is make sure you're moisturizing your hair as often as your hair needs it. with each handling, at the least, but if you style your hair daily then you should moisturize it daily to prevent breakage. your hair is most likely dry. and therefore requires a moisturizing treatment, which you can do with each wash to restore the moisture that the relaxing process stripped from your hair.
you were on the right track with the flexi rods
so once you've cut the damage and starting implementing protein and moisture treatments to re-strengthen your hair, the next step is to minimize handling (low manip. and choosing of proper, protective styles to that end, such as buns and updos...and even flexi rods, perhaps.) styles that you can keep in for at least about 4-5 days but ideally longer, until your hair gets back on the right track.
hair that is healthy should not easily break. ideally you should strive to see no more than about 10-15 broken hairs per detangle session and no more than about 5 per styling session, given that your hair is relaxed.
also, this is a given, but curb all direct heat use. using flat irons wll surely make your hair's health worse. keep usin the flexi rods, and when you want a more straight look, try a roller set that you saran wrap. they have tuturials of youtube, esp. Sista with Real Hair on YT. she only uses heat once a month and always wears her hair straightened. she uses roller sets and saran wraps to style.
good luck, and let us know how it goes! i think most ppl on BHM only check the forum about once a week to every two weeks, while others like myself who may check it once a day (because i have no life lol
jk i am a full time senior who graduates next semester, a wife and mother and i work full time, but i get hardly no sleep because i'm an insomniac) primarily lurk. sometimes it takes a few days for people to get around to seeing posts. usually when i post, i don't really check for a few days for responses. and then too, if a thread isn't viewed enough, it'll get lost in the abyss. that's happened to a post of mine- couldn't find it anymore. it has to be resurrected through viewership. it's daunting, but...eh.