I have been experiencing lower back and hip pain for 3 weeks and the pain is increasing and worse when I am sitting.

See below. There are many causes of low back pain and hip pain. Often they are related. A bad hip can cause buttock, groin, and/or thigh pain. Sometimes a pinched nerve in the back can cause back, buttock, and thigh pain depending on which nerve is involved. If your pain does not improve or gets worse you should contact your physician to help identify the cause.
Multiple. The source of your discomfort may be from your uterus, Ovary, to Herniated disc in your lower back. Have you had a recent injury or been doing lifting? Need to see your primary care doctor for initial evaluation.