How do i overcome the embarrassment?

ok, so iv been with my guy for almost 4 years now, and he wants to try anal .... i used to do it regularly with my ex, and i always really enjoyed it... but 1 time (and this is SO embarrassing) when he pulled out, i pooped a little :( ... my ex didnt make a big deal out of it, but for me it was so humiliating, i wanted the ground to swallow me up ... i dont know why it happened, i didnt feel like i needed to go to the toilet beforehand or anything ... i havent had anal since that happened, and id really like to do it with my current boyfriend as i always enjoyed it in the past, but im scared of the same thing happening again