Hello, and I hope I can help you today. First of all, in the first month of use, all birth control pills will cause some degree of side effects of bloating, breast tenderness, nausea, mood changes and irregular bleeding. This is because when you first are taking the pill, your body is still making its own hormones so essentially the hormones on the pill are sort of tricking your system to make it think that you are pregnant. This is why many women get symptoms that are sort of like pregnancy in the beginning when they start the pill. However, burning with urination and back pain are not usually due to side effects of the birth control. These are actually symptoms of urinary tract infection, which can happen to any young woman when they are dehydrated or sometimes after sex. Urinary tract infections require a urine test that needs to be performed in a doctors office to determine if you need treatment. So in your case, I would recommend continue to take your pill and trying take it as close to the same time every day as possible will hopefully make your breakthrough bleeding stop. However, I do recommend you see a doctor or other healthcare provider to get your urine tested to make sure you do not have an infection, as if he urinary tract infection is not treated it can spread your kidneys and make you very sick. I hope that I was able to adequately answer your question today, and that this information was helpful to you. Best wishes, and I hope you feel better, Dr. Brown