I have been on depo for almost 5 yearsl now...since I was 17. I take a break after 2 years for a year, then go back on..and repeat.
Symptoms I got were breasts tenderness in the first 3 weeks...loss of period symptoms, slight weight gain.
Everyone is different...When i got my first shop, i lost my sexual desire. Took a break after 2 years..got my period after 6months, was irregular for 4..regular for 2...and went back onto the shot. My sexual desire didn't change after that shot..it was even better!

breasts got tender...and was just a cry baby for a while haha.
IMO...if you don't think you'd remember the pill..and don't want a child for a lonnnggg time...definatly try out the shot. I know girls that forget their pill for one day..and get pregnant. Also take a calcium supplement..as depo has shown to increase the chance of bone loss in women...
Hope this helped!