Varying cycle lengths?

My last cycle was 32 days long. I’m currently on CD 24 and tonight I was having some cramping and spotting. It feels like a period is on its way. Took a pregnancy test and it’s negative. I’ve been having positive opk’s the last three days so I’m a little baffled here. I know 32 days falls under a normal cycle length but 24 days is also considered normal. Can cycle lengths vary without there being an underlying issue?