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If you had unprotected intercourse
then these symptoms are quite suggestive of possibility of pregnancy
You should have been regular with the Depo and when you knew you are late then you should have had barrier precautions; Now being afraid would not help. Delaying may be more traumatic if you do not want to keep pregnancy.
Please get home urine pregnancy test to be reasonably making sure you are not pregnant.
I hope this information would be both informative and helpful for you