I just felt like I was recovering from a massive car accident or huge surgery at the time- even though it wasn't
Can I just say, give yourself some credit! 50 HOURS of labour! Another human being pulled out of your nether regions with an instrument, requiring a cut which subsequently got infected, and recovering from all that while being expected to look after aforementioned helpless human 24/7 with no break before the job began? Car wreck is an apt description, imo. That's not easy by any stretch of the imagination.
Not to mention the crash of hormones that occurs after birth, the lack of sleep, the pain, aches, leaking everywhere constantly, the sheer terror of being in charge of keeping a baby alive (!!), I could go on.
It's a lot, even without severe injuries and complications which I would say you've experienced.
And the heavy feeling imo was probably your pelvic floor being knackered after the ventouse and epesiotomy. I hope your have healed up by now op, bit it might be worth seeing a private physio who specialises in women's health, if you need to.