@boxing23: What do you do for cardio?
Is i long sessions or a HIIT style training session?
Maybe try to only do HIIT cardio in short sessions, that will aid your ability to stay fit and preserve your muscle.
And add deadlifts to your workout, they are arguably one of the best all round bulking exercises and strength gaining movement anyone can do, regardless of your slight frame/weight.
And just eat more mate, its pretty simple, I call it eating like an adult as you know whats good food vs bad food, so eat lots of good food and that will help you grow.
Good luck mate.