The bleeding means your hymen is now gone. If he only rubbed the tip of his penis the first time, you are on birth control, and he used a condom the second time...(and as long as the condom didn't break or slide off).. then you don't need to worry about being pregnant. You can still buy a pregnancy test from the drug store to ease your mind.
The bleeding is from your hymen ("cherry") breaking and causing a little bleeding. This is just internal tissue trauma, and has no bearing on pregnancy whatsoever. The birth control method you're on is called depo provera (which is a long acting shot that lasts for 3 months), not the "drop shot" (just for your future reference so that other people know what you're talking about).
If you used a condom in addition to having an up-to-date depo shot, then you're fine. If you want to have a period, you can consider going on the pill, the patch, or the NuvaRing, which will let you have a period so you can monitor things more closely.