FIT ATHLETIC SO

Since I've met my SO 3 years ago I have put on 50 pounds I just can't seem to get out of this funk I hate the gym I use to love it now it gives me anxiety and I try my best to eat healthy but some days I just slip I also work and when I leave I just want to go home and crash. My SO loves my body thinks I'm beautiful but lately he has been hitting the gym hard and looks awesome (body builder status) and now I'm a little insecure. I know I need to get back in shape does anyone have good advice on what motivates them to stay in shape.