Hi need diet advice!!

Hi everyone!!
New to this app and have been hitting gym for last 8 months, really need diet advice as that's my downfall and halting progress! I had PT for six months but he didn't get my long working hours and fact I was so hungry following his nutritional plan!
So here's my dilemma
I work long hours as a nurse, I get up at 0430 and walk to local train etc ( 30mins ) and get to work for 0700, I start my day with black coffee and porridge however usually add toast peanut butter too as so hungry, I then have lunch at wrk typically egg/tuna salad with pudding , tea I have jacket spud with tuna again, I snack so bad! I do try and have fruit but sometimes it's impossible as I need sugar hit-I work till 8pm and it's BUSY! My PT suggested upping protein which I did try however only have access to microwave , I'm not budging weight despite going to gym three times a week doing cardio and majority weights/strength traing, my weight is 62kg I'm 5ft5 , my legs and arms are mega toned-it's my stomach that's the problem area !
I ve seen posts on meal prepping and feel this is what I need to do-but no clue where to start!
Any advice massively appreciated!