Hello,
Birth control pills can cause depression as side effect. You can change thr birth control pills or switch to other forms of contraception. If the symptoms persist then depression needs to be ruled out. You will need to incultate certain lifestyle changes and choices that will help you through the rough times and may prevent depression from returning. Try to identify and focus on activities that make you feel better. Motivate yourself to do things for yourself. Don't isolate yourself socially. Take part in activities even when you may not want to. This will uplift your mood and wellbeing.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
What pill you on? Maybe you should think about switching it? ?