Hmmm. To me, this translates literally from Irish as "I do a lack of interest", meaning "I'm not interested". Obviously this is synonymous with "I don't give a shit", but I've never heard this used to mean "I'm having a shit".
Having said that, if you asked me what the Irish for "I'm having a shit" is, I'm not sure I'd be able to tell you.
The pronunciation of déanaim neamhshuim would be along the lines of: day-nim nav-him