Sounds like break-through bleeding - sometimes happens on progesterone treatments. I know I had it a fair bit when on depo and implanon, similar sort of description too.

You've said you don't feel that you can really talk to your GP about it - can I ask why? Because if it doesn't clear up, gets worse, starts to smell funny or your period doesn't arrive, talking to your GP and getting it checked out becomes really important. It is definitely worth the effort and time to find a doc you're relaxed and comfortable with, especially if you are considering pregnancy.