I don't know about a single SVN command, but this seems to work:
svn log ${SVNURL} | awk '$1~/^r/ && $3=="username"{print $1}' | tr -d r |
while read rev; do svn diff -c $rev ${SVNURL}; done |
awk '/^\+\+\+/ || /^---/ {} /^\+/ {a++} /^-/ {d++} END {print a, "additions"; print d, "deletions"}'
Use your username instead of "username".