Fiber can help but its never a significant factor in improving BM’s in my experience. Acacia Fiber is my favorite though.
I’ve never had constipation in my life until my long run with anti-biotics. Constipation is now one of my worst symptoms.
What I’m doing currently is supplementing S. Boulardii yeast + diet. This is working for me, although I’ve heard it can cause constipation but that has not been the case. I’m taking between 15-30 billion a day.
You need to stop using stimulant laxatives like Senna. I wish I was told about enema kits (about 7.00$ on amazon.com) a long time ago, these work great and are very safe in my experience. Not only will they help tremendously with constipation, you can add pro-biotics, Boulardii, etc. I don’t use them every day/week like some people do but they are safe if done correctly.