TMI but need advice on caster oil

ok so went to the doctor yesterday everything looks good with my little man and hopefully we'll be seeing him in 13 days but when doctor asked if anything new or concerning I explained that I haven't had a BM in 5 days even tho I'm still on my softeners and laxative that she prescribed, cause of this I'm crazy uncomfortable my back feels like its ripping apart, its causing non stop non progressive contractions and insane gas. I've been pounding the water bottles and basically been living off fiber so doctor told me go home, get some castor oil, make myself a smoothie and go to bed. In her words let it do its job. I haven't tried it yet tho cause I'm kinda scared can't this stuff bring on contractions? Is this safe? Am I gonna be living in the bathroom for the day? Is there a safer option? I mean she is my doctor but I'm not sure I'm comfortable with this idea.