Brown spotting 4 days before AF

Kath • Mother of #1 Jay-Levi my rainbow🌈 💙my baby girl Emily-Jane born sleeping😞💔currently pregnant with #2 😍❤️
I spotted last night some brown discharge. It only happened once but I've been having mild cramps mainly in my leftish side, boobs are slightly sore, had a bit of nausea but not in my belly kind, just feeling so strange I'm very confused, if that was implantation bleeding when could I take a test? All comments appreciated girls ❤️