I brought some XL tena knickers from boots online. And some size 22 black high brief knickers from Asda
Last time I just got the black full brief ones from Tesco
The ones I’m wearing now I know will do me post partum again. I’m wearing size 20, M&S full briefs and they’re brill. M&S also do full briefs period pants which work well with a pad over for extra protection.
If you want ones to catch the blood then I recommend the period panties from primark. I'm small but I've definitely seen larger ones. Maybe have a look and see