Get out of your comfort zone and make yourself go with the trainer. You can do this and once you do it you'll think"Well that wasn't so bad". Then it's easier for next time. I am the same as you but I've been trying to kick myself out of my comfort zone cuz I notice I get more confident with myself. Good luck
If not, 8-10 lbs hand weights, doing squats and lunges, sit ups, push ups. Any of those can add to your routine