We have been dating for almost 3months now I don't really doubt him but we have many thing uncommon to each other and I am sacred that he will leave me one day because of that any advice on how to make sure that his the one?
No. Only time will tell if you are good for each other or not. You didn't mentioned which kind of differences between you both. Were they related to long term life goals like buying a house, adopting kids or how do you spend money? Those differences will only get worse over time, in my experience such a relationship it's not worth the time and effort you spend in. Usually there is no thing as "the one". There is just people you spend some time with : A year, five, twenty... You'll find more than one during your life. That doesn't mean the second or the third one is less important than the first one.