Struggling with work

I'll be 7 weeks on Wednesday, but since 3 weeks I've been slowing up at work; before I know I was pregnant.  I'm struggling to work 8 hours everyday considering I'm constantly queasy and can't really eat, let alone keep up running around the kitchen (I'm a cook). In the last week if had to call out once, be sent home early twice and take break every other hour, I've came so close to fainting three time already. I want to ask my manager to cut my shifts to 5 hours but I'm afraid of telling anyone I'm pregnant considering I've had a miscarriage in the past. Any suggestions?