Could Severe Itching And White Vaginal Discharge Be Due To Yeast Infection?

Alright so I m a 20 year old female and I am not a virgin. I have had 5 partners and have been tested and checked for stds after each one except for recently. I had sex with a guy and the condom had slipped off. He told me not to worry that he was clean and since I was on birth control I felt a bit at ease. a few days later I got super itchy and a milky white discharge (this was a month and a half ago). 6 days later I went to the clinic to get checked for stds and infections and nothing showed up. She told me there s a bit of yeast present (I get yeast infections very easily) so I used a yeast infection medication (monistat).. the thing is, the next night there was bright red blood in my underwear. I had missed 2 birth control pills (non consecutively) and figured that was the reason why, but the next day there was no longer bleeding. Now, the day after that, I had masterbated using my finger in the bathtub (therefore well lubricated) and started to bleed. I m extremely nervous now. Should I get re-checked? Could it be an STD or is this just a series of unfortunate events... thank you for your time.