Here are some things to consider that'll tell you whether you're a strong candidate:
1. What ECs were you involved in before deciding on medicine? Adcoms love non-medical ECs. If you were doing stuff during this time (fresh-junior years), it won't be a problem that you're getting your medical ECs in now.
2. What made you sure you wanted to do medicine before having done the medical ECs? Did ECs help you decide on medicine or are you just doing them because you've decided on medicine?
3. Lots of people decide on medicine later in life. And they've gotten in. I don't know how much of an effect late ECs will have on your app, but they shouldn't hold you back.
4. Quality/duration of med ECs are important. Shadowing for 5 hours and volunteering for a month isn't gonna cut it. You need to show some kind of commitment to these activities. On your AMCAS, you'll need to explain how they've helped you grow, strengthen your desire to practice medicine, etc.
5. MCAT/GPA are essential to determine if you're a strong candidate. This process isn't all about the numbers, but they're pretty darn important. Have you taken the MCAT yet? If not, study hard.