I Had Protected Sex And Also Checked For A Break

I had protected sex and also checked for a break or leak afterwards, nothing of the kind. Its been 4weeks since. I've also missed my periods this month, the last date being the 4th of december. Since I'm late quite often and was also under stress and had a change of routine and diet, I gave it sometime and then had regestrone twice a day for 5 days under prescription. Its been 2 days since and I'm still not down. If I have a test now will the medicine mess up the results? What would be a sensible course of action now? Could I have a medical abortion now without my parents having to get involved? Is it costly?