Had sex yesterday at 8am (bf came inside) on tricyclen, (10th pill day). I am bleeding thin blood unlike menstrual fluid w.O odor. Pregnant? Cause?

Not pregnant. It is too soon to show any signs of pregnancy, and unlikely with oral contraceptives taken correctly. This is some form of break-through-bleeding, but its cause is indeterminate.
Possible but... Any time you have irregular bleeding, you should do a pregnancy test. Having said that, what you did yesterday won't show up today. It would be positive from a previous act. Also, it may be that your bcp's need adjusting. I'd recommend doing a pregnancy test and then calling your doctor as he/she knows your history.