Here's what you do and I guarantee success.
1 buy a scale of you don't have one already
2 download a calorie track app on your phone
3 weigh yourself every single morning after you use the bathroom but before you eat or drink anything and record it
4 record every single thing you eat and drink all day every day.
After a month or 2 of this it will become very easy to see what your calorie requirements are and you can adjust your diet accordingly