That's why you feel it in your lower back. It is a high risk for injury.
You have 3 options:
-figure out how to set up with a neutral or slightly arched lower back, which may involve higher hips as well
-switch to sumo, since many people are unable to set up for a conventional deadlift with a neutral spine and sumo makes it much easier
-or finally just keep pulling like that and hope you don't blow out your back. I would strongly recommend against this though, especially since you aren't moving any significant weights yet.
Watch some "how to deadlift" videos on YouTube
Note to people posting deadlift form check videos: there is no point posting videos where you are pulling extremely light weights like under 70% or less than your body weight. It is easy to have good form with light weights so the only thing we can judge is how you set up. In this case however, the setup is the main problem.