Why am I like this?

Let me first say I really am looking for honest opinions,I feel as I age I may be going through a mental struggle that I have no way to get help for.Im 20 years old Ive only been in 2 relationships my Ex and my Current.

I got with my ex when I was 17 and he was 26.He was the manager at my work place and Although I know now its not right,My 17 year old mindset didint.Which makes me feel stupid everyday for being so naive.. He was a jokefull guy which made me like him,he'd comment about other girls and it didint bother me before we officially got together then I would just secretly be jealous and not show an ounce of it unless it was serious..

Fast forward to now im with my current boyfriend he just turned 19 and I always said I liked older guys because there more mature but my ex proved me wrong on that one🤦Anyway I've been being super immature lately pretty much half our relationship..I can't seem to stop being jealous..in the beginning of our relationship he was open about his celeb crushes or past life crushes etc (I was his first)he also had a really bad wandering eye and would look at any pretty girl that would walk by even if I was right next to him..This would piss me off!Id either be silent or be straight up to him..

But now its like OUT OF CONTROL!

I get jealous of every pretty girl that happens to either walk by or even be on the tv..Its gotten to the point where my boyfriend has to secretly reassure me everytime a pretty girl comes on tv which makes things worse..I just feel the tension when a girl is involved in our relationship in anyway...Like today he happened to scroll past this girl dancing on instagram and he stayed on the video i could see in the reflection on the mirror and that made me mad

I know he walks on egg shells and he 100% shouldint have too but it just makes me mad hes attracted to other women Im not insecure I've lost more than 100 pounds people say I'm pretty all the time..(not to be conceited)Or maybe i am insecure.I just dont get why im likes this Please help.