Wondering if i'm possibly pregnant due to symptoms?

i'm 29 and db is 37. i have a 4 and 1/2 y/o son from a previous relationship. we are ttc, so that's the reason i'm so curious to see if i am. past 2 weeks i have had these symptoms: lower backaches, cramps, nausea, cravings, EXTREMELY sore/tender and swelling of , constipation, gasiness, lots of mood swings, insomnia, sluggish, sometimes have lost train of thought, bloating, and that's basically the symptoms I can remember right now. I have not been on bc since december last year, so i know i don't have to worry about my body getting used to not being on it. we were using condoms, but stopped last week of july. last period was around 8/16. lighter than usual. (only 2-3 days instead of a week) i thought i was on period yesterday, but just spotted and today i had a very dark brown discharge. i am NOT on health insurance as of right now, so don't have a doc to go to. took a pregnancy test yesterday and it came up negative, but as soon as i wiped was when i saw blood (geez,..sorry for being so graphic). am i taking the pregnancy test too soon? do you guys think I could be pregnant? we really want a child! thanks for reading this ;)