Sorry to hear you're having such problems, and hope they moderate! I've been pretty lucky with the Plaquenil, a bit of lightheadedness, but that's been about it.
Have you tried taking ginger as a supplement to help settle your stomach? Ask your doc first, of course, but if she/he says it is OK, try up to about a teaspoon (or take the capsules). For the diarhea, you poor dear! I've heard that fiber actually can help - by helping regulate the bulk. Again, ask you doctor.
I know that the side effects FOR ME moderated with time - and mine were mild from the start. Actually, I was so glad to go on Plaquenil - it helped me feel so much better!
Hugs, and keep us posted on how you're doing!