Bleeding after birth

Hi all, I had my baby girl on the 16th July 2020. I had a 4 week bleed afterwards then a period at 6 weeks. Since then my period cycles are very short. Ranging from 12 days to 20 days with an average of around 18 days. I’ve had a clear smear, a thyroid check and an internal examination. All came back fine. I was wondering if anyone else has had this issue? We are hoping to try for a 2nd baby in the summer so I’m hoping it’s not a fertility issue. I have to add I stopped the pill in Oct 2018 after 19 continuous years on it, started trying for a baby Jan 2019, fell pregnant in the April then MC in the May. Had to wait 3 months to try again then fell again in the October. Had a wonderful pregnancy and a natural problem free birth with a healthy baby girl in the July. So I’m a bit puzzled. TIA X X