Cutting back hours?

I’m curious if anyone has any experience with trying to cut back hours in a union environment? I work for a factory that has union set rules as far as hours & overtime. It’s seniority based and while I have some seniority, I happen to be the lowest foreman in my department, so I get stuck with all the overtime. Right now we are working 7 days a week with daily overtime (10hr days), in addition to shifts on Saturday and Sunday (8hr days)... last week I hit 56 hours and this week I’ll be closer to 65 and again next week... between working 7 days a week and so many hours I’m starting to get extremely exhausted. Unfortunately, since it’s a union I can’t just ask to have my hours cut back... I’ll be 31 weeks next Wednesday and I have a dr appointment on Thursday, so I’m considering asking him for a note. I just don’t know how to go about it at work... I’m so tired and starting to get panicky because I can’t get anything done and baby will be here soon.