35 weeks should I ask for maternity leave from my job??

Isabel • Mommy to a 3 year old boy!
I've been working at HEB as a bagger for about a month now and I get really bad cramps and Braxton hicks while working so much or carrying a heavy load. I just don't know if it's too soon to ask for my maternity leave since I'm 35 weeks. Should I ask or just keep working? Help!!