Rx for good ECs:
1) pick something up that you'll do consistently but with not a huge commitment: e.g. hospital volunteering and/or shadowing a few hours a week. at my UG, you could sign up for 3 hr shifts once a week in a variety of services.
2) Take on something eles thats more like a pet project (e.g. will only do on a handful of days but will require greater effort). Great examples would be volunteering as a camp counselor at camps for kids with diseases, going on a medical mission somewhere, volunteering at child free-immunization drives, etc.
Ideally, ECs are things you've sustained for a long time and things you can link passion/experience with medicine. Both are great to talk about in interviews, but things like camp counseling or medical missions are much stronger on essays (typically).