Overtime when pregnant in tx

My job is doing mandatory overtime, thats 10.5 hour days. This is week 2 and im utterly exhausted.....i sit all day in an office at least but my back hurts, my eyes hurt, my head hurts, im coming in early and leaving late i mean this is to much. Another pregnant lady at my work doesnt have to work but she is due in 2 weeks, im 23 weeks. Anyone know the tx laws about ot? Do i have to work???