Hi Clare,
Well the answer to that would have to be yes. It is only 6 weeks since you birthed Max and it usually takes between 5-8 weeks for your period to return after birthing.
It is very *usual* to have a very short luteal phase for the first cycle or two after birthing and it is also common to have annovulatory cycles.

Did you do an opk to confirm you ovulated or did you chart?

After all of my mid trimester losses it has taken 2 weeks after birthing to have a negative hcg. I know some women take longer but for around the gestation you were at it would be around 2 weeks too.

So, I am not sure what your test means. If it is very very feint and you are definite about ovulation having occured then perhaps it is a evaporation line.
Of course it is possible also that you conceived.

I am sorry I can't help but I hope you will let me know what your line means...