Advice needed please 🙏🏼

So my last period was 4th June, I have a average 30 day cycle give or take a day or two.

Cycle day 18 I started getting a little lower backache which I get when I start my period.

Yesterday on cycle day 19, I started getting some light pink spotting which I’ve still got today. It’s not heavy only when I wipe and not every time.

I have on/off cramps & low backache like I’m about to start my period anytime now.

My partner and I had sex a few times a week ago but only came once (sorry TMI)

Please if anyone could give some advice, I’m feeling so confused as I’ve never had this before.

Thank you so much in advance x