Unless i'm mistaken, My Posts gives the list of your posts sorted by time. however, it doesn't show the latest post, if someone else posted after you. for that, you can put a tag on the topic the post is in, then look at My Tags. unfortunately, that doesn't show who posted last, so it could just show the last thing you posted, which you probably didn't want to look at again.
to make a long story short, i wish that when you look at My Tags, it would show who posted last in each topic in the list; i don't have a good enough memory to look at the time of the last post & determine from that if the post was by me or someone else.