Brown blood?

So my daughter is 9 weeks old I had my period when she was 5 weeks. The last few days I've had whitish discharge and a weird smell.

Two days ago I started spotting and now its brown blood, is this normal?

I started birth control a week after she was born and then switched to the depo shot.

I've been feeling super weak and just not myself and a headache.

I've had sex 3 times in the last 3 weeks. I'm paranoid. What's wrong with me?