According to the information given, you state that "I started my new pack of Trinessa last Sunday". By last Sunday, do you mean Sept 06 or 16? If you started it on the 6th, which ideally you should have after your period on the 3rd, and missed it for 3 days thereafter, then the contraceptive effect is not there. Also, it will result in intermenstrual (in between 2 periods) spotting.


This is what probably happened. This can also be due to withdrawal bleeding, which happens with TriNessa.


If you began the pack on the 16th then it is definitely a cause of concern. It can be an implantation bleeding in both the cases as the contraceptive effect is not there.


Please use an alternative contraceptive this month as a precaution if you do not want pregnancy as you will have to wait to get a pregnancy test done.


You state that, "I don't think this is breakthrough bleeding from missing pills because normally, I don't start until my 4th day of inactive pills anyway". Breakthrough bleeding is different from the bleeding you have on the 4th day of your inactive pills. The latter is your normal period.


If the bleeding was not due to the effects of the pill then it could be due to STDs like Chlamydia, gonorrhea, and trichomoniasis, cervical polyps, yeast infections, endometriosis, cervical dysplasia which is a precancerous condition, uterine polyps, uterine fibroids and cervicitis.


It is difficult to determine the cause over the internet. Please consult your gynecologist. Hope this helps. Take care!