apparently, I don't know the comma rules

so my awesome writer boyfriend read thru Blood of New Beginnings and I came to realize that I don't know the comma placement rules. most of his corrections were comma placements. at first I laughed, but then I thought "man, I really don't know crap about grammar rules." how can that be? how did I forget all of that stuff? I mean, I'm a writer(don't even get me started on writing analytical papers for school because I suck according to my professor) and I use grammar allllll the time. however, I don't think I'm using it right.the bad news is I'm going to have to brush up on basic grammar rules so my edits aren't so painful.
the good news is he really liked BONB and that meant a lot to me because he and I write completely different genres.