Hello and welcome!
With certain medications, it takes time to build up in your system and it also takes time to get to the proper dosage. You may feel better in a few days or a few weeks. If nothing changes, even when the medication dosage is upped, you may need to try other meds. Sometimes it takes time to figure out what works for you. There is not one drug that helps everyone all of the time.
In a side note, the meds Will only help with the symptoms associated with BPD (I.e. anxiety, depression) it will not help the BPD itself. You should also try DBT/CBT to help you understand your thought process and how it works (out doesn'twork).
Hopefully this helped. Feel free to contact me if you have questions.