Have Constipation Since Childhood. Taken Laxatives. Defecography Shows No Puborectalis Dysfunction. Colonic Transit Test Required?

Hi , I am having constipation science my childhood. I used to use my finger for evacuation.I used to have complete evacuation though. Just 2 years ago it became very difficult for me to pass motion and I saw some significant amount of blood coming out in my stool.Then I visited one GI and after so many many test I have diagnosed with anismus. First I started taking osmotic laxative and started Biofeed back session .It was ok for some time like two or three months but after that it is almost the same.I stopped osmotic laxative and started on naturlax.I have attended many biofeed back session.I have seen my condition improving at least in the lab, but not so much in the toilet .I have to pass motion multiple time in the morning,so that it becomes little manageable.So I thought that I will try botox injection and came to a better GI institute in my country to consult.They ordered defecography which is already done and the result given by radiologist is that no puborectalis dysfunction another test is colonic transit test. I am not really sure that why this is ordered because first as I have already traveled to a different place other than my base location I am anyway little bit more constipated than usual,second I used to have complete evacuation in my childhood ,so I think there should not be any problem in motility.Should I go for this or should I try to consult some other doctor to see if botox can can be taken. Cause I feel that this test is time consuming and even if slow motility comes out of it that proves nothing.some other time it may come even worse or better. what do you suggest?