I need answers or help!!

The blue on the picture above shows where I’ve been getting small cuts under my vaginal opening for about 2 months now. Nothing else is causing it except for sex. I’ve used a lot of lube, monistat, and I’ve been tested and nothing has come of it. I’ve even gone without sex for 2 weeks! When I am having sex it is very painful and it feels like it’s burning on the inside. I would really like to know if anyone has answers!! I am on nexplanon too, I’ve been on it since March but this started in July.