Welcome to HCM.
You are suffering from early heavy menstrual bleeding.
You did sex after ending your period.Also you are on Trinessa
birth control pill and use a condom.
So possibility of pregnancy
is almost nil.
It is probably due to adverse effects of Trinessa which are quite common more like early or delayed menstrual cycle,irregular spotting,breast swelling & tenderness,headache,vaginal itching
If your bleeding persists more than 10 days or other symptoms develop,then consult with your doctor to evaluate underlying pathology and need some clinical examination.
Wish you better health.