I'm currently going on 7 weeks postpartum and i'm having slight abdominal pain and foul smelling lochia discharge which went from brown to now light pink. is this an infection?

It may be, however you have not given adequate information. If you have fever, the symptoms are getting worse or not improving in a few days seek evaluation. There are mild infections that the body may be able to mount adequate immunity to combat and there a situations that you may need to be on antibiotics. It is important to ensure adequate rest to allow your immunity to be strengthened.