How Early Can Pregnancy Be Detected In A HPT?

Hi, my husband and I haven t been trying to conceive long, but this is my first time trying to conceive ever. It s been 12 days past my suspected ovulation date (2 days until my suspected period date)and at 10 dpo I bled brownish red spots. Since I ve studied a bit of pregnancy and childhood development while in college I thought maybe it could be implantation bleeding. The timing seems in place, but I haven t gotten even a faint line on a home pregnancy test. The spotting hasn t shown up today, but the cramps are ever apparent and just as strong as they were the night of 10 dpo when I first noticed the spotting. I was curious what my chances were to get a positive test? I haven t had any symptoms besides bloating and this cramping and indigestion as far back as 4 dpo. My period is still normal from being on birth control back in my teens, but being almost 21, I m concerned that maybe I m experiencing fake symptoms. I m wondering if it s possible to get negatives at 12 or 13 dpo and then get a positive at around 14-16 which would be the day my period starts or two days later.