PCOS: Metformin and Spotting

Hello! I just started Metformin on March 28th and had sex on March 30th. After sex I went to the bathroom and notice spotting. It’s so light that I usually have to look for it when I’m using the bathroom. Anyways is this normal? I had my wellness exam about 2 weeks ago and everything wad fine expect for high insulin levels and having the irregular period and being diagnosed with PCOS. The spotting is very light. From my Apple Watch my predicted period starts on April 5th. So I’m not sure if I spotting due to the potential period coming up.