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In sexually active females of your age it is very common to have Urinary Tract Infection
and also if your cycle dates are near by when you gave sample may be the reason of RBCs in the urine sample.
As burning sensation was there ,what you can do is just give a clean catch repeat sample if these are not your cycle dates or if yes give sample after 3-4 days. If infection comes then Urinary specific Antibiotics may be required for you.If normal just take care of your health.
In the meantime drink plenty of fluids if possible crineberry juice. It will help to flush urinary system
Advise would be to have protected sex as it is safe.