Need immediate advice. Should i leave her already?

Alrite so me and my gf have been together for 28 months. Its been long distance for a while now. We've never really had any big issues till she got to uni(3 months ago). Now she's just a very different person. She's cold, she's not as caring. She still loves me, or she wouldnt cope with it. But i cant stand it. Its the 2nd time in a row she didnt rmmr our monthaversaries. I know its not a huge deal, but she'd ALWAYS rmmr these little things before.
She doesnt text me when she's out with her mates. She gets pissed at the smallest things. She's not as sweet as she used to be. She's always enjoying, when she KNOWS im miserable, but she doesnt do ANYTHING to make me feel better. Also on her birthday i got her a coash watch. I gave her the receipt with it incase she would want to change the gift. She asked me before doing it, and obviously i wouldnt FORCE her to keep the watch i got her, so yeah she changed it and got a bag. Who does that???!?!?!?
This has been going on for too long
She made a mistake a month back when she lied to me and partied when she said she'd be at her friends place. She felt guilty and told me about it. I got REALLY mad, but i did give her another chance. Everythings just changing so much and im NEVER happy anymore. She's made me so paranoid, so jelous, so miserable, but im so in love with her, and i just DONT know what to do.

Sounds like she's already moving on from you, you'd probably be best served to start going your own way too. This is a quite common occurrance when people move forward to the secondary part of their life (university).

If you're not happy, why stay together? If you're in love with someone who makes you miserable and upset it sounds like you're either codependent on her in some sort of way or afraid to be alone.

There are some on this forum who have some experience in LDRs (more than me anyway). So perhaps they can shed some light.

Because i REALLY love her. At this point though she's been changing SO much that i dont know if its her that i love, or who she used to be.
I talked to her about it, and she saw where it was going. She started crying so much, and I just dont know what to do.
I love her ALOT. She's my first love, but im just unhappy. Im miserable. The distance kills us, and im always paranoid. I dont know what to do anymore