Post partum ovulation?

Ok so my youngest son is 6 weeks old, my bleeding stopped around 3 weeks pp, still no period. I am mostly pumping and occasionally nursing him, but no formula. My older boys I did mostly formula with some pumping, so i have no clue what to expect. I also got on an iud after the first one and a tubal ligation the same day my second son was born. Had a reversal in march of 2016, took 7 months, 1 round of clomid and an iui to conceive my 6 week old. Not doing birth control this time as i turned 30 this year and i dont want to wait long to start trying for the next one.