New pill and bleeding

Okay, so I started using the pill in November. I was nauseous for a lot of the first 2 months. The third month wasn't as bad. But then on my 4th month, my doctor prescribed me a different brand of pills because of my insurance. So I started this brand of pills mid-January and 2 weeks in I started seeing light brown blood. Very light spotting, don't even need to wear any type of liner but it's shows when I urinate. It's been going on for 6 days straight and my period isn't supposed to start until next week. What is this bleeding? I never had that problem on the other brand of pills. Assuming is breakthrough bleeding but i don't know if anyone else had similar experiences? Please share. Thank you!