I began filing Married filing separately. My husband informs me that we can file jointly. Will I have to start over and lose the information that already the inputted?

No need to start over!

To change your filing status you're going to go to the Personal Info section on your tax return (both desktop and online). Under this section, you'll navigate to ?You & Your Family. From here you'll want to look for Your Filing Status and click Edit next to Change Your Filing Status.

Hope this helps!