Possible STI or my birthcontrol?

Hi, I’m wondering if I have an STI or not. I don’t have burning when I pee, I’m not itchy or burning either. My discharge was been wonky all day at one point it was clear with streaks of white and now a few hours late it’s this. I am having slight cramping but it’s very light sharp pains. I do have a copper iud and I’m quite confused. Yes I get regular checkups with my gyno he looks and it seems that everything looks fine but maybe it’s not? I’m not sure but this looks a little yellow to me and It doesn’t smell bad.