In addition to your own health there's a possibility baby may be poorly after the birth too. When I had my dd we were both still in hospital at the point you'd be getting married.
So with that in mind my recommendation is actually to bring the wedding forward if possible. Weirdly you'll probably be feeling better and be better able to cope before the birth than right after.
Regarding a dress, weddings are an area I used to work in. One dress that prove very popular with pregnant brides but will not be around now but hopefully you can find something similar, was an empire line dress with sheer overlays that were pencil pleated creating the image of narrow vertical lines so it draped over the bump gently without straining against it - just an idea - also wouldn't sit on or irritate any c-section scar
Also just an idea - if you do go ahead with the post birth wedding you could have a red wedding dress, dresses come in all colours now even if the advertised image is of it in white/ivory etc look at the detail of the various dresses online and you'll often find they are available in a variety of colours. I've seen and dressed brides in amazing dresses in red, blue, purple, green, deep pink, even orange (I wasn't such a fan of that one but the bride loved it and the colour held special meaning for the couple)
Red is actually a fairly widely available colour for wedding dresses now.
Also ensure you have a good BRIDAL seamstress to make any alterations necessary - note it's easier to take a dress IN than it is to let it OUT so err towards too big rather than too small. Non bridal seamstresses tend not to have the skill and experience needed to handle such delicate fabrics and aren't often experienced in working with the shapes of wedding dresses, I've also dealt with many a bride desperately trying to find a last minute dress because a high street seamstress who normally only deals with everyday clothes has messed up their dress! A truly skilled seamstress can alter sizing, change the neckline, add/remove sleeves and straps, balance the shaping and work wonders generally! The seamstress I used to work with (sadly retired now) once altered a wedding dress to make it easier for a disabled bride to not only put on in the first place but be able to manage various medical devices and toileting on the day with minimal help needed from others and still look "traditionally bridal"
If you are still bleeding a lot come the day instead of relying on mere pads - which can leak and slip etc - I'd recommend you get period pants or at least tena pants as there's a larger area of absorbency and they're easier to remove by tearing down the sides rather than trying to remove normally and risking catching blood on the dress. Again also a good seamstress if you advise them of potential issues may well be able to come up with solutions and alterations for you.
But as I say I think bringing the wedding forward might be a better option for you
I'm very sorry for all your losses and heartache 