Dear somewhatironic: Congrats on your new baby! So sorry you have had to deal with these birth control problems while caring for all the needs of a child.
You are absolutely right. This is not a "real period". Unlike birth control pills/patch/ring where the homrones leave your body within five days, the hormones in DepoProvera can stay around for MUCH longer. The synthetic progesterone in Depo (and its long lasting metabolites) can delay the return of regular ovulations and regular periods for a couple of months.
In terms of the type and color of flow you are having, when the bleeding is brisk and heavy the blood flows quickly out of the uterus and vagina. When the bleeding is scant and slower it has a much longer time to be exposed to the oxygen in the air. This exposure will turn the blood color brownish. Think about a piece of meat which has been exposed to air for a while. The outside will be dark brown/gray. Yet when you cut into the meat, and expose an area which has not been in contact with the air, the color will be red.
It is very common for women using birth control pills (BCPs) or Depo to have a bleed which looks more like dark motor oil sludge than bright red menstrual bleeding. The synthetic progesterone in BCPs or Depo creates a thinner lining inside the uterus. This creates a decreased amount of flow. This more scant flow will appear as a dark brown color, and thick consistency.
Should you be at risk for pregnancy, that should be ruled out first with a reliable pregnancy test--especially if you are being sexually active without another form of contraception.
Bottom line, I would urge you to contact the OB/ GYN or clinic that was giving your Depo shot and let them know about your continued spotting/bleeding. They may want to rule out an infection or discuss other forms of birth control to stop this erratic bleeding.
Yours,
Jane