Will a 6 week break erase all of my progress?

im an ectomorph. I’m naturally super skinny. I’m 5’9, and started out at 115 pounds. I’ve been working out for the last 18 months and put on about 20 pounds, but still have a long way to go. I’m having jaw surgery in October so I won’t be able to workout for 6 weeks and I’ll be on a liquid for 2 weeks and soft foods for 2 weeks after that so it’ll be a month before I can even eat regular food. Will that 6 week pause completely erase my gains? how long will it take to put it back on?