Possession can even occupy the mind: You do
understand how restriction can kill a relationship like glass seal
over candle flame, but you are unaware because of the nature of
your personality, it doesn't demonstrate outwardly, therefore it
retreats back inside your soul and clings onto your mind. This
force jealousy to poison you indirectly and weakens you ability to
hang onto the relationship and makes you wanna give up your
relationship because of this.
If you noticed, the cusp of the problem lies with you, not him. If
you are saying that because of his personality, he flirts around -
that will be another issue altogether. But because he is just being
himself, this characteristic of him has already been there since
Day One when you knew him. So this is a classic case of the Seventh
Love Law: Love brings up everything, unlike itself - where you are
forced to face with unpleasant issues you didn't realise/felt it
doesn't matter in the beginning.
You NEED to grow from your flaws and evolve your
mindset. Please note that IF HE WANTS TO LEAVE, he will
leave IRREGRARDLESS of
whether there is another girl or not. Because you see him as
an emotional dependancy and whenever that 'him' seemed to disappear
with another woman who you felt that she could have see him as an
emotional dependancy as well, you are violently shakened and
couldn't find an alternative source to hold on. Why feel this way
when in the first place, this personality of his is defintely part
of the subconscious factor why you would fall for him.
No confidence in yourself equates no confidence for the
relationship. When you do practice the importance of respecting
personal space, understand the theory as well. If not, it's time to
have a good private talk with him and let him know, so that both of
you can adapt and compromise with one another.
P.S: Relationship is a bond with another person - so learn to speak
and don't keep things inside. Are you a Cancer, Scorpio, Pisces?

Cheers