Yes. Huge red flag.
First of all, you say he is very agressive about it. That means he doesn't care about your opinion about huge life decisions. In his mind dating you for a month gives him the right to make these decisions for you.
Second of all this is a tactic frequently used by controlling abusive jerks. They want to get you pregnant ASAP to seal the deal. It's harder to leave someone you have a baby with, and even if you do you're never completely rid of them.
These kind of controlling partners often also take control of finances. They may encourage you to move in and quit your job. Pregnancy is a good excuse for both. They promise to provide, but when you're unemployed, without a home of your own, with a baby to take care of, you're utterly dependent. You can't leave without figuring out a way to provide food, shelter and medical care for your baby. Many women take abuse in exchange for 'security' for their kids.
Pushing for a baby this soon isn't romantic love. It's a trap.