How can I be ready for a possible break up?

Well first off I love her.. and she loves me. We have been together for 6 months. We were recently in a nevermet situation but we recently met a week ago. She was very happy and said she wanted us forever! But I can feel her slipping away from me. She has done it before but that was because I couldn’t see her. Now that I can idk what’s going on. I asked her about it and she said, “Idk what it is.” But then a couple of minutes later she says that I won’t lose her.

I don’t think she can do this. Ill have to go back home in 5 weeks. I know i can do it. I have the motivation to fight forever for her, but I feel like I’m sacrificing everything, and doing everything I can for her just so that she can leave me later on. I Don’t want her to leave me and I promised I wouldn’t leave her, and I wouldn’t if I didn’t make that promise anyway because I am to in love! I’m regretting that we met and wishing I just found someone in person from the beggining! (Ik I could have, but I am shy.) It would’ve saved me from all the pain I am going through now.

How can I be ready for a possible break up? What’s your guy’s best method? What should I do? What would you do? And if you guys have questions for me, ill answer all. Btw, Thanks in advance guys!