What Causes Abnormal Vaginal Bleeding With Abdominal Discomfort?

Hi so I have had discomfort in my stomach and went to the doctor on Thursday and they said I had a lower uti and got medication. I was also on reclipsen birth control and stopped taking it 2 days prior going to the doctor. I started bleeding that night very light the next day I started bleeding heavily and got scared so I went to the er and they told me the same thing that I had the uti and prescribed me different medication so I stopped taking the other one . But they never gave me a clear explanation for the bleeding. It is now Tuesday and I m still bleeding not heavily but the blood is bright red. The abdominal discomfort is still there idk if I should be concerned or not ? I was reading and the bleeding could possibly be because I stopped the birth control but I don t know .