Can a internal ultrasound detect ovarian cancer? or at least show if there's something suspicious going on ?

Yes, but: A transvaginal ultrasound(US )and or abdominal ultrasound can often detect enlargement the ovary in ovarian cancer. However screening US are not recommended as there are many conditions that can cause ovarian enlargement besides cancer, most all of them benign. The most important approach is to check US in women with persistent unexplained abdominal or urinary symptoms.

Yes,: it can detect ovarian carcinoma. If the ovaries are well visualized, the ultrasound is very sensitive for detecting ovarian masses that might be cancer. However, there is significant overlap in the appearance of benign and malignant ovarian masses, so the US cannot make a definitive diagnosis, and if an ovarian mass is detected, further follow-up, additional tests, or surgery might be necessary.