Hi, I Am 21 Years Old. I Have Been Having

Hi, I am 21 years old. I have been having lower abdominal pain since Saturday night and have not had a bowel movement since Friday night. The past two nights I have woken up with pain in my lower abdominal and my left side which then leads to me being nauseous and having cold chills. For the past month, I have also been having dizzy spells and nausea almost everyday. I am on LoEstrogen which is a type of birth control and I have tried taking Advil to help with the pain in my stomach but it hasn't helped. I was wondering if you had any ideas about what could be going on/what I should do next?