Is taking birth control pills 100% safe for unprotected sex? even if i ejaculated inside?

No...: In medicine and life, nothing is 100%. But theoretically, it's, and doing nothing will have no consequence, namely, 100%. That is life. Of course, safe sex and caution against std should be exercised all the time. Meanwhile, it's worthwhile to keep this fact in mind: life is a process of constant struggle to cope with reality, certainty, and uncertainty of daily living. Best wish...