First of all, congratulations on your new baby
I am sorry you had a bad experience, but yes, the magnesium can be quite terrible. I had it with both my pregnancies and I got away with just feeling yucky.
Try to take it easy (if this is possible) and remain vigilant, as you have been, in case you keep feeling poor, as preeclampsia does not always quite end with delivery. My BP was all over the place postpartum despite medications, and my headache was worse too. I called my docs daily
My c-section scar healed pretty quickly. I moved around a lot (within the allowed limits), but also took the pain meds, which helped too.
MC 3/2009 and 3/2011Henry
(1/1/2010-1/7/2010) - forever loved and missed; severe PE with Hellp; partial placental abruption, classical c-section at 25.6 weeksMatilda
(Nov. 2012, born at 35.4 weeks) - severe PE
Our pain has been put into words, placed into empty cradles, to remember that all our babies lived, that they mattered and always will. - Field of Cradles http://www.fieldofcradles.org/