Thanks for the query.
Sometimes urine pregnancy
test kits can give false positive results in conditions like:
When result is read after 3 minutes
When more concentrated urine is used
When the expiry date of the kit reached etc.
For more details:http://srsree.blogspot.in/2012/06/causes-of-false-positive-pregnancy-test.html
Your symptoms could be side effects of depo or can be part of menstrual syndrome.
As blood test
for pregnancy is negative the chance of pregnancy is very less.
The symptoms will subside soon if not you can take symptomatic treatment after consulting your doctor.