I need bc for 6 months. Which is best?

I recently had a miscarriage and after 6 weeks my hormone levels still hadn't gone down properly and I was diagnosed with a pregnancy of unknown location. This is where there is retained tissue but it was so small they couldn't see it on any scans and due to a major pain in my right side it was suspected it was ectopic. As a result I was given the Methotextrate injection to kill off the remaining cells and have been told I must not get pregnant for 6 months to be sure it is out of my system. Which bc methods do people recommend that won't take too long to get out of my system once the 6 months is up and I can ttc again?