Here is the official website that explains the Family Medical Leave Act:
First of all, is your company big enough to even be required to provide it? There have to be at least 50 employees, so many small companies are exempt.
Then, if your company is required to provide it, you should be able to use it intermittently...but you do understand that the days off are without pay? And while a company isn't supposed to fire anyone for using it, they will likely try to work around it and fire you if you take off too many days, even intermittently, especially if you don't get your job done, or if your absence puts a greater burden on your co-workers.
No, the reason for the FMLA isn't to extend sick leave for YOU, necessarily, but to allow you time to care for others in your family who might be ill. If indeed YOU need the time off, you might need to be thinking about ways you can ask for "reasonable accommodation" to do your job, under the "Americans with Disabilities Act", or ADA --
but then, you would have to declare your disability to your employer, and indeed, disclose what your limitations are.
From your post it sounds like your human resource person is confusing the FMLA with the ADA, and is asking you to comply with the requirements of the ADA, which can be found here:
You also need to understand that the ADA isn't a job guarantee either. While employers are not supposed to fire you because you have a disability, they can and will fire you if you cannot perform your job, even with reasonable accommodation. And it will be up to you to figure out what that reasonable accommodation might be, and get your employer to agree with it.
These are very tricky laws to comply with, and as I said earlier, not all employers have to abide by either of them. You probably need to read them both carefully, and consider your job situation, before trying to invoke either of them in your situation.
...I am not a doctor, nor health professional, and don't pretend to be one, here.....