I've been in the exact same scenario and left my job after about four months. It didn't impact my future job searches at all outside of hiring managers saying "Hey, looks like you left that job fairly quickly, why's that?" All they needed to hear was that it wasn't a good fit and that I was sold something different during the interview process.
If you feel like there's still potential with the company you're at, be straight with your manager and tell them how you're feeling diplomatically. Otherwise, I'd start sending feelers out elsewhere.
Assuming you left your previous job on good terms and want to go back, reach back out! I've been at companies where people boomeranged back ranging from a few months to a week. It's not as uncommon as you think.
If you feel like there's still potential with the company you're at, be straight with your manager and tell them how you're feeling diplomatically. Otherwise, I'd start sending feelers out elsewhere.
Assuming you left your previous job on good terms and want to go back, reach back out! I've been at companies where people boomeranged back ranging from a few months to a week. It's not as uncommon as you think.