ok so i have been with my bf for 3 years 8 months, (almost to the date) and we actually just broke up

i told him it was because i was not happy, which i wasnt... i was then talking to my older brother and he asked me if i wasnt happy with my bf or if i just wasnt happy with my life at that time, that got me thinking, i started a job in January and am currently working there i really hate it tho, it is a job as a waitress, working with annoying coworkers who think that just cause they were working at the restaurant for 5 years that they are the cats meow, i hate having to wait on ppl hand and foot and getting crappy tips all the time, i served for 5 years of my life, and i cant take it anymore, the only problem with quitting my job is that the money is soooo..... but ever since i started there i started to be miserable, i started to be irritated with the smallest stupidest things and my relationship with my bf diminished.... then it tured around and things that he did would annoy me, everything that he did... so now my problem 2 days ago i broke things off with my bf and have been miserable every since, so is my brother right? was i really just not happy with life and it had nothing to do with my bf and i made a really big mistake? should i start looking for another job? im so lost and brokenhearted right now

so if there is any suggestions or comments id love to hear them