Maybe I was born to get cheated on in every relationship

I don’t think so.

Just ask yourself the question, if I were dating myself, would I cheat on myself

There could be a number of reasons why someone would cheat on you

1. Small private parts
2. Mental health issues
3. Rude and Disrespectful
4. Ugly and Unattractive
5. Poor
6. Overweight/Obese
7. Low iq
8. Bad family
9. Weak masculinity
10. Fearful and Scared

See if you exhibit any of these traits and work on it.

For small private parts, try working out more to boost your testosterone

For mental health issues, try getting help from a Psychiatrist or counselor

For Rude and Disrespectful, try taking classes on how to be more mannerful or practice manners with a family member

For Ugly and Unattractive, try focusing on personal hygiene and working out. Also buy nice clothes to put a good impression on yourself

For poor, try working harder at your job and asking for a raise, working in another sector of your industry, or try dipping your toes into new sectors like real estate

For overweight/obese starting working out and eating healthier

For low iq, start eating more brain foods such as walnuts, working out so your brain gets more blood flow, and challenging yourself by doing puzzles or playing board games

For bad family, try talking to your family about why they need to respect you and/or your partner

For weak masculinity, try working out and building muscle. Be confident in yourself

For fearful and scared, get treatment from a psychologist or from a trusted friend in order to become more confident and open to challenges

Overall just be yourself, be confident, workout to become a more manly person, and look good to show that you care about yourself.
I can assure you, no one will cheat on your if you are a kind, sweet, handsome, strong, and hard working man.

How long does your short story have to be? let me know.