2 days late. Light brown Discharge. Neg HPT.

I’m officially on CD 35. I have NEVER had a cycle this long. My cycles usually run anywhere from 25-32 days, with an average of 28 or 32 days. 32 days is the longest it’s ever been. This morning I noticed small amount of light brown discharge only when I wipe. No other symptoms although my breasts are sore and I’ve been tired. I’ve taken HPT’s but they all appear to be negative. What could it be? When should I test again? Is this just a weird very late period fluke? It can’t be IB right?