can anyone tell me what this is?

sorry for the TMI, and it's not actually yellow color that's because of my flash. but I've been having this for the past two days and I don't know what it's from. I've had sex during my ovulation week three times and once the day before ovulation and on the 27th I used preseed. but I don't know if this is a good sign or not or why I'm having it? first time trying after my miscarriage last year. can someone tell me if this is a good sign or why I'm having it please