Anyone else??

Even though i can sit and take breaks in between customers at my job the back pain is getting to be alot and im only 20 weeks... I already got a belly band and its still not helping much. My grandma told me i can already stop working if i need to (i live with her) but i feel so bad about quitting because i want to be able to buy my son everything on my own (me and my bd are split up and hes not helping at all) im just feeling so guilty about wanting to stop working already. Its still alot of standing and by the time i get home i can barely walk from the back pain. What should i do??