Please, please don't panic about this. I had this after my first birth and I spent weeks feeling devastated about it and googling non stop. After two births I no longer have it or have any lasting issues. HVs and midwives had little to no advice, but after extensive research I have lots I can share!
What you have is extremely common but not a lot of people talk about it, or in fact know they have it as they don't look down there. If it's your bladder causing the issue, it's known as a cystocele. They come in different grades. They're the cause of women weeing when on a trampoline for example, lots of women have this issue.
Just after birth your hormones still feeling everything is quite relaxed, especially if you are breastfeeding.
It will likely improve over the next few weeks as things move back up inside. If it doesn't completely go, all is not lost and you can improve it somewhat.
• Once youve been signed off to do exercise, do exercises to improve your pelvic floor. This is more than just kegels, look on YouTube for postpartum pilates or specific pelvic floor workouts. Your core, glutes and hips all need exercising in unison to bring everything back up
• Also look up hypopressives which works on elevating your insides, which also improves a cytocele.
• Book in a "Mummy MOT" with a practitioner near you, a specific postpartum check where they give you an internal exam to review your pelvic floor
• Limit any lifting of heavy things for at least a few more weeks, this causes you to bear down and can make symptoms worse. Put baby in pram rather than carry in a carrier as often as you can
• Eat lots of fibre so you don't end up constipated and pushing when you go to the toilet
• If you're breastfeeding, contemplate feeding lying down during the night so you're not sat up all the time (Lullaby trust has good advice on how to do this safely)
Three weeks is nothing yet, and honestly things do massively improve by the 6th month mark. Hope some of the above helps :)