Depo after effects

So I got my last depo shot in like October or November 2015 and I didn't wanna go back to it bc I had gained a lot of weight... So I've lost like 20 lbs since I came off of it... And it's been on and off since then to small periods to crime scenes down there... And now I'm 4 days late according to eve... And I've been pretty active sexually... But I'm just wondering if I should get checked out or if there is a kind of birth control I should try.... Please help!