Need swim advice just 7wks to IM

Just 7 wks to 1st IM attempt & my L shoulder is worrying me.  I'm slow (~2:20/100M for mile+) with no real swim background before getting into tri 3 yrs ago.  This yr's swim vol is only ~130kM. Over summer I've had bouts of what I think has been mild "swimmer's shoulder".  It seems to get better when I back off.  Hoped decreasing my swim volume would rest it enough to resolve.  I did good (for me) 4k straight pool swim 3d ago (1:32 & pretty fresh at finish).  Then at this AM's swim the shoulder was sore/tired again & I altered my hour workout to less distance (2250M) & more easy drills.  This PM the shoulder feels fine.

Not surprisingly I breathe to my right, although I can bilat breathe some.  Been working on breathing every pool session entire summer so  doubt I could become fully comfortable breathing left in just a few more weeks. 

Prob will not be able to sustain the 10+k/wk swim vol in my training plan during this peak phase without risking irritating the shoulder so much I miss my IM.  I know my stroke needs help long term, but short term I'm trying to get through that IM swim 1st.  Should I take a week completely off to rest the shoulder (tough during peak phase), or maybe cut back to just swimming enough to keep my BOP stroke together until my IM?