Went off program and gained 19 pounds

As if yesterday January 3 I’ve been back to logging my intake and staying within a healthy calorie count. I gained back 19 pounds of 90 pounds I lost since falling off the wagon in the beginning of October. I’m back and already am down by 2 .5 pounds in one day. The important thing is I get back to where I left off 3 months ago and not keep gaining it back.