Is Pregnancy Possible Despite Taking Depo Shots And Plan B After Sex?

Question: Depo shot at 14 weeks one day- Question:

I've been on the depo-shot for one year and four months. Prior to that, I was on the Mirena IUD, after the 5 years I had it taken out and got the shot the next day. Therefore, I have had no periods for roughly 6 years (some spotting here and there). Recently, my Dr went on vacation and I was unable to get my depo shot (his office does not carry it, I need a script then I go in to get the shot by an MA). I had my last shot March 1st and should have had my next shot on May 24th (12 weeks). Instead, I had it on XXXXXXX 7th, making it exactly 14 weeks and one day. My boyfriend and I used a back up method (as we always do to be extra safe) on XXXXXXX 7th around 1 am (we only had sex once during the 12-14th week b/c I was nervous) . We used a condom but it broke and we did not realize until afterwords (he ejaculated). So, to be safe the next day I went and got the one step Plan B pill. I took the plan B pill 12 hours after intercourse & was able to get my depo shot hours later. My Dr and the pharmacist said I should be fine as there is a two week window period you can be late for your shot (14 weeks max). Is this correct? Since then (12 days) I have taken a pregnancy test that has been negative. I had some minimal spotting but no period, which is to be expected since I haven't had one in so long.

My question is, what are the chances that I am pregnant? Also, we are currently using condoms to be be safe (we have both been tested for STDS etc). How effective is the depo shot without condoms? Since I had the shot almost two weeks ago, am I protected against pregnancy? I will take another pregnancy test in a week.