Working while pregnant?!

I work about 30 hours a week so not rly full time or part time, but I’m 29 weeks now and working is becoming more and more dreadful by the day. I love my job and most days once I get going I’m okay, I also don’t want to not work and sit at home all day and let my mental health decline because I know boredom’s and loneliness are my biggest enemy! When Is a reasonable time to start cutting back at work?