Spotting

Hi ladies, so my period is very irregular, last time I had it was once in May and once in June, haven't had it since(yes I took preg test in between then and now, all neg)
That's nothing out of the ordinary for me. Anyway, I have no clue when I'm due for a period obviously. I've been SO moody lately, on edge, tired, etc. I figured either my period was coming or pregnant(I wish!) I've been like this for about a week or so now. Yesterday I had some light pink spotting, nothing today now. Last time we had sex was the middle of last week. Does this sound more like period spotting or could it be implantation?
When should I test? If I don't get my period.