Moving from pre-vet to pre-med is certainly possible, but there are a few things you need to consider:
1) I believe some vet schools require the MCAT, but a vast majority require the GRE. Meaning...it's very unlikely you have studied for or have taken the MCAT, which is entirely different from the GRE. This should become priority number one for you. Start figuring out when you should be taking the MCAT and come up with a reasonable study schedule based on that time line.
2) What is your GPA right now? Depending on your GPA, some GPA repair or an SMP may be required.If you were competitive for veterinary schools, it's fairly unlikely that there will be any drastic changes, if any, needed prior to applying to medical school.
3) I have two recommendations for gaining clinical experience for your application: scribing and volunteering. Scribing is paid and is more clinical-intensive than volunteering, but both will get you the direct patient contact that you need. Most hospitals have a volunteer program. As for scribing, simply google scribing programs and pick one.
I should also mention that general, non-clinical volunteer experience is general paramount to medical school applications. I'm not sure how much of this you've done in preparation for veterinary school, but it's certainly something that you should consider before tossing out medical school applications.