issues after breakup!

[ts1234]

ok soo its been about 4 months since my ex girlfriend broke up with me.... ive been very up and down about it all... at times im like screw her she was not the one for me and the next day i am sad and depressed for awhile again..... i really dont understand why we broke up , we had one of those stupid fights that meant nothing right before she went home and then she just called me and said we were done......i of course was devastated and confused... she was really my first love, and we had dated over a year and it really was perfect for the first 8 months ...i did anything and everything just to make her smile because it was worth it to me but it all changed when she had gotten a new job and gotten more friends.... i felt like she as drifting away months before we broke up but she assured me everything was fine so i went along with it( im only 19 so i didnt see these signals that said to leave her ).... she wouldnt put time towards me and like wouldn't commit to me 100% and we hadnt had a date night in 2 months .... i had only seen her for a few hours a week and i only dealt with it because i loved her and i just knew she wouldnt leave me because i believed everything she said. like every little thing still to this day reminds me of her and i hate the fact i still feel this way, i feel like i shouldnt even be bothered by this anymore and yet i still hurt... and what made all of this even harder was the fact that after she broke up with me i made an attempt to fix it all and get back together, she of course had already found someone else a few days after the breakup which in my mind explains why she had stopped spending time with me and putting in effort that last 2 months... after that failed attempt and no contact after a month , i hear a knock at my door and it was her... she wanted to get back together and i was beyond shocked and felt like we were suppose to be together and told her that i was going to think it over... but i then found out that she had kissed someone else and hungout with them the enitre time after the breakup and yet she said that she had been missing me like crazy since she left....i didnt believe her and i knew that then she was just using me and i felt like she had gotten whatever she wanted from that other guy and pressed resume on me......she had put me through alot and i know i derserve better and yet even when anything cool or something big takes place in my life i like immediately want to tell her what was going on because i was so use to telling her everything that i forget that she is gone... im still depressed and cant find a way to go to sleep happy at night and i think the reason as to why it is so hard is because i had a very sentimental attatchment to her.....( if that makes sense) ..i just dont know what i need to do to get over her...... i dont know why i feel like im still missing out on something with her even though i know it is over.... ive done anything and everything you can think of.... i started working more hours, focusing on my fire academy even more,even devoted a ton of time to the gym by eating right and bettering myself each and every day ( and now she goes to the same gym and at the exact same time as i do) and i took up new hobbies and nothing finds relief because in the end i just want to tell her about it all, any advice would be appreciated, thanks