recovering from back surgery

i had a question about swimming and recovering from back surgery. i just wanted some input from anyone that is in or has been in my position. i am 30 and had a microdiscectomy in december 2007 on l4/l5. i was a competitive swimmer until college and that's when the back problems started. ok so enough with the boring stuff, i have finished therapy after about 9 months and i began swimming again. my questions are more related to fears about rehernaition as i am not really sure how my back got messed up so bad in the 1st place. do i need to be worried about reherniation by swimming hard or doing flip turns, or really anything i used to take for granted in the pool? i have had some back spasms this past week on my 'good side' so i am beginning to worry a bit. its been tough because i literally think about every step or movement i make on dry land because i dont want to end up back on that operating table. as you could imagine its stressful :) any input is appreciated.