I'm in the UK but originally from the U.S. If your baby still needs some additional medical care (or you need some extra recovery time yourself), you might be able to get some additional weeks of family medical leave from your employer. It would probably depend on whether your doctor thinks there is a medical reason for it and will support it and on what kind of worker you are (full vs. part-time, big company vs. small company, etc.) whether you technically qualify for leave. But if you do qualify, you can take up to 12 weeks a year. I'm not sure if the maternity leave you've already had counts as part of this allotted amount (depends on how your employer organizes their leave policies, etc.), but you should at least be eligible for an additional 6 weeks. Unfortunately, it's highly likely to be unpaid, unless your employer offers paid family leave, or you have vacation time or sick days accrued and you can use these. But at the very least they have to protect your job during those 12 weeks. Honestly, I'd be in touch with your employer, especially an HR person if you have one, and talk over your options with them. I think in these situations, the best approach is just to be honest with a trusted person at your job and try to figure out a solution. Most employers do what to work with you if they can, though they might not always want to pay you for those days off, which might be difficult.
Here's info from the Dept of Labor: https://www.dol.gov/dol/topic/benefits-leave/fmla.htm
Hope that's helpful.