You can't. That's why there is what we call trust.
get a new boyfriend
When he is your EX-boyfriend and you are over the relationship. Let your heart be your guide.
get another boyfriend and make ur ex boyfriend jelous
Forget HIM!!!! Go out and find you another guy to date! Act like you don't care, that will drive him nuts! My personal opinion is that you can do much better!
If your boyfriend starts to stop showing affection towards you and is always busy and going out instead of being with you. These are signs of your boyfriend cheating on you.
Everyone forgets something, usually because the mind is occupied by another thought so you tend to forget
For going to another country
there might be one
Forget about it. You are not going to like everyone in your life, but you need to be polite and respectful. She could become your mother-in law.
See if he flirts with another girl, or if there are rumors going round about him fancying another person, ask him about it!
by going to another country
Of course he is going to be mad