You're not alone!! Very often I have struggled with motivation and it would make me feel very down. I'm hard working, not lazy. So why did I struggle so much with focusing and making myself sit down and study?? I can't really say why since I never utilized student counseling services like others suggest, but it sounds like a great idea. What I do know is what helps me stay motivated. Sometimes undergrad classes feel pointless. What doesn't feel pointless to me? Working at a vet, dog training, volunteering at a shelter, doing anything that relates to vet med, etc. By just being in classes I tend to lose focus on the end goal and it's draining. You need to find what makes you tick and what makes you want to study. It's different for everyone. But I know what helps me is being involved in activities that inspire me in my career field and having my ideal study environment: a lit candle, natural light, and instrumental music (usually video game soundtracks).
I hope you find what works for you and that you know that many of us struggle with motivation. It's not always easy to figure out what works, but it's doable. Just because you are struggling now does not mean at all that you do not have what it takes to do well in vet school or as a veterinarian.