If I remember correctly, my first menses after giving birth to my first child was very heavy too. You can just observe the next few cycles for now:)
I’m also a BF mom and menses came on the 10th month. Take a few more months to monitor the cycle too. If it’s abnormal, visit your gynae.
Possible.. dont worry.. check again on next few months.. also check your menses cycle is 28 days or 30 days etc
I just had my first menses 7 mos pp. It was also heavy, too heavy that I had to change pads almost every hour.