Brown Discharge Days After Sex

I had sex on 01/30 with my husband and a couple days later (today 02/01) I have had cramping and brown egg white discharge. I ended my period a week ago today. Could this be old blood? I am not on the pill but we used a condom. I asked my husband if the condom leaked or broke and he said no, that he checked. I am freaking out.

Can implantation happen right now, or within two days of sex? Or could this be ovulation?