Tired of thinking and need advice !

I m a girl of 20 years old, student, i have been in a relation with my boyfriend from 6 months ago but i know him since 9 years , he's 29-30 years old.
I passed before him by many many failure in my relations and never been comfortable and happy with someone like i am with him.

A month ago he had to travel for work issues, and in the same period of month he was there i quit my job and had a lot of emptiness in my life.
Two weeks or more i started to stress and have bad thoughts and doubts about him : do i love him? is that love or habitude ? what's love anyway ? do i want him ?
And those ideas are stressing me and confusing me because i know deep inside that he's the one and we already talked about future plans , but im afraid of those ideas , and even if i was with him and saw a cute guy i get angry and feel like why im looking ? i feel cheating even with a simple look and no intentions ..
I even go angry when thinking about my X-boyfriends that been long time i haven't thought of them until now , like why im thinking of themm????

i stopped eating and i feel stressed because i dont want to think of all that i was so so so happy for the last six months i dont want to ruin my relation with him or lose him , im afraid of losing him , i dont want that but i cant stop thinking and i think i need a way to go out of that mood and bad ideas.

Please help.
Best regards and thank you