HELP (Question about Depo)

Okay so I may be freaking out too much, but I went to an OBGYN yesterday and talked to them about birth control. We discussed Nexplanon which I'm totally okay with, but it takes a while for the insurance to clear it and she wanted to give me time to think about it as there are so many options and I have never been on birth control before (I'm 19). In the mean time tho, until I make up my mind, she said she could give me a shot of Depo as kind of a backup until I make my decision. I got the shot. Now here's my question: since it was 10 days after my period and if I wait the 7 days for it to "kick in" so to speak, what are my risks of getting pregnant from having unprotected sex? I'm in a long term committed relationship and we usually use condoms, but I'm sure y'all know how it goes when you're in the heat of the moment. I know obviously the shot is 99.8% effective but a lot of stories I've been reading are like "I got pregnant right away after starting the shot and waiting [insert number of weeks here]" and it's freaking me out. There's also the possibility that I'm ovulating because [TMI] I noticed a lot of clear discharge this morning. Any help/personal experience stories are very appreciated.