Heavy bleeding a little over two weeks after giving birth

I gave birth 17 days ago and I feel like the bleeding has been normal all the way up until now. Two days ago it started to lighten up and then all of a sudden it became very heavy, with clots even. Clots haven't been massive, but the heavy bleeding is starting to worry me. Is it normal for it to go from lighter to heavy like this? I have been active like going to the store and such, but I've been taking it easy since the heavy bleeding started and it's still heavy. Should I call the doctor tomorrow (it's a weekend) or does it sound like its normal? I did have a second degree tear and I don't know if that would make bleeding worse.