Could I be pregnant? Hoping for a BFP.

[Hopeforlilfeet]

Would like to know if I could be pregnant. First of all in September I took my first injection of depro. Due on the 15th of December (13 weeks later). Throughout my depro I had no changes in my body and my body ovulated each month going by my cervix and discharge. AF came 26th-30th in all three months and lasted moderate for 4 days (normal). Trying to conceive I had unprotected intercourse; 28th, 29th, 30th (Nov); 4th, 6th, 7th, 10th, 12th, 14th, 17th (Dec). Going by my CM, cevix and calander I ovulated within 9th-13th. Morning of 21 st I had what could be described as implantation bleeding. Started out pink then turned brown (never spotted before). Although described as Implantation bleeding it finished night before the 26th (day AF is due). Since then I have had pains in my lower abdomen, diaphram and back (upper and lower), headaches, hunger, queasy (sometimes throwing up), moody and  strong fatigue. All symptoms on and off, but frequently at night.27th I woke to "snot like" CM, checked my cervix today and found no signs of AF and the positioning to low (meaning barely reaching with my longest finger), as well as hard.

I did take a test but came up BFN on 23rd. Wondering if I should take another? Or just signs of depro leaving body?.

Hoping for a good answer for my partner and I. :)