infection or std? please help

So I got a yeast infection a month ago, after having sex without a condom, and I'm pretty sure it was a yeast infection because there was white discharge and LOTS of itching...I didn't take any medications but it's been a month since then...the discharge is gone but the itching is not going away. I tried probiotics and cortisone creams but it's not working. Also along with the itching I'm noticing these reoccurring cuts in the creases of my Labia. Is this an STD or a result of itching too hard? I usually notice them after itching pretty hard, they go away within a day or less...and i also noticed this whitish brown buildup/residue in my labia...it's NOT discharge it's only there in my labia...it sometimes looks like dirt when I wipe it...it doesn't have a strong smell...so what do I have and how do I get it treated? Please help me guys 😢 thank you