I'm 8 Months Pregnant With My 5th Child. Ive Always

I'm 8 months pregnant with my 5th child. Ive always had constipation issues where I would go months without having a BM and finally when I would they would be huge and rip me. After my last daughter I found a way to stay regular. Everything was going great up until 2 months ago when my regular routine stopped working. I'm really uncomfortable but I'm really scared that when I have another BM it's gonna hurt really bad. I wish there was something I could do that would turn my feces into diarrhea instead. None of my doctor will help me. They keep telling me to do things that aren't working. I'm not to take any kind of
Laxatives though. Is there anything I can do or use that will keep it from ripping me when it does decide to come out? My doctor seems to think that because of the baby getting bigger and all my organs getting squished. I'm scared and dreading when the time comes I don't want to do it but I do. So the question is what can I take that would cause the feces not to kill me when it comes out. Thanks! BMiller