You need to go to tech school for at least 2 years if you want to be a certified vet tech. And even 2 years is pushing it- I have had a ton of credits every semester (16-18, and even more next semester). The curriculum is demanding, and there is just no way you could learn it all in four months. Even after earning your degree and passing the board exams, there is still a lot of training required to get you settled in and taught the 'ways' of the particular practice you work at. Some people say being a vet tech is almost as hard as being a vet- we do a ton of skills that vets don't always do, most importantly restraining, and also ear cleaning, nail trims, dental cleaning, wound cleaning, sutures and suture removal, surgical monitoring and assisting, wellness exams, client relations.... the list goes on and on and on! Vet Techs are an essential part of a vet practice and they need to be well trained!
I would not trust in the skills of someone who became a vet tech in a mere four months.