Q: How do I know what to do regarding my transmission and should I not be driving it?

My car wont move in drive. It will move in 1st,2nd &3rd .when I'm in 1st it takes a while to move I have to slowly ease on it because it revs high in rpms so I let the gas go and keep tapping it until it's no longer shuddering and is time to shift to 2nd gear. When in second , most of the time it works just fine, just slips and loses rpms so I let go and press on it again and generally works just fine after that. 3rd gear I never have a problem with it drives smoothly as if nothing were wrong with it. When this began , there was a small leak I noticed which I was confused by because we replaced the tranny about a year ago. So I immediately got the fluid for it and a bottle of stop leak and haven't had any leaks since and the fluid is bright red and seems clean. There are also no service lights on. This is my only transportation at the moment and don't know what I should do. I have been taking it easy w/care. I just need to know where to start as of now. Thank you so much .

My car has 137000 miles.
My car has an automatic transmission.