TwoLoves - if you think planning a wedding is stressful, fast forward your life 15 years, add a mortgage/bills, kids (if you so choose...), in-laws, etc., ad infinitum...stress is probably my main drinking "trigger" and it sounds like your fiance is the same way...
I would not be presumptuous enough to tell anyone I didn't know personally what to do (and I rarely do it with the people I do know), but I would encourage you to slow down and take a step or two back and assess things. If you're feeling like red flags are going up already, it might be a sign...