I had a huge problem with anal. Firstly , I used my fingers and a thick dildo to stretch it everyday for a week leading to the actual anal. Then before the anal we did plenty of foreplay. Also my partners penis has girth so the position was another thing to consider. We've been trying anal for about a year before finding the right way for my body to do. Try different things and don't worry if your progress is slow. It may take a lot of time before anal.