If i only had one depo shot, when should my period start again if i missed my second shot?

Hard to say: Depo Provera (medroxyprogesterone) can disrupt your periods for many months. After only one shot most people would have their periods return to normal within 3 months but it could be up to 6 months. If you have been on it for several injections, it can take up to a year for periods to return to normal.

Possibly: Women respond differently to even 1 shot of Depo-Provera. Some women become amenorrheic (no periods) quickly, some develop irregular bleeding, while others have no change or variations of above. Some women remain amenorrheic for up to 18 mos even after just 1 shot, while others never stop getting their periods or regain menses quickly. More importantly, you are not protected from pregnancy.

Varies: That will vary from person to person. You can no longer rely on it 3 months after your last shot. Some start menstruating after others take up to one year.