Help- positive OPK but I’m coming on my period?

Anyone had this before?

So I’m like 99% sure I will have my period tomorrow as I’ve got a fair bit of brown discharge and cramping which is what I usually have before a period and my temp has dropped low.

But I just did a opk and it’s positive ?!

Anyone had an LH surge before a period?! Thought maybe it was ovulation spotting but with these cramps and the way I’m feeling, I know it’s a period and the brown is starting to go a bit red (sorry TMI!!)

I don’t ovulate every single month and I’m irregular so that’s why I thought I’d take the opk.

My weight is what is causing my lack of ovulation regularly and I’ve since lost 1.2stone to try and get them back on track and this is possibly the first time in years that my cycle has been between the normal length range (if I do come on tomorrow!!) just curious about the positive opk....

Thanks x