I can not comment on after birth issues as not been there yet but what you are expalining sounds EXACTLY what I have only just recently recovered from. For the space of probably 2 or more years I was terrified of going to do a poop because the pain was the worst thing I had ever experienced, I used to literally scream and cry, it felt impossible that I could actually get it out! (Sorry TMI)
I was too embarassed to seek help for the first year but when it showed no hope of improving no matter what creams I used I HAD to go or I swear I would probably have actually tried to stop going tot he toilet.
I saw a consultant who diagnosed anal fissures and very small internal piles near the exit which were getting 'rubbed' each time I went to the toilet nad the fissures would just keep splitting each time I statred to poop which then created the blood and pain.
I was given Lactulose to try and softent he poops and also given vaious creams, some steriodal but nothing seemed to work or keep it away, I had the best luck with using Betnovate which healed it up but then as soon as I stopped using it, it would reacure again. I gave up with the consultant because he told me that the only way to heal it after all that had been tried I would need to have surgery on my sphinta (not sure of the spelling) but after doing some research and finding out it can cause incontinece and not actually a gaurenteed result I have decided to say a firm no to that.
I ended up just using a baby (non parfumed) wash for my bum, drying it properly and wipeing gently after going to the toilet.
Drinking lots of water helps too as it softens the poop naturally and keeps you hydrated.
I also used a cream ment for sore nipples from Tesco I think it was a camamile one which I found soothed it slightly.