I (30 m) am feeling highly anxious about the girl ( 25 f) I started talking

I started talking a month ago with a girl online. She is travelling out of country therefore we couldn’t meet. During her trip she and I talked a lot about different things, make a lot of jokes, in jokes even talked about being together . She started sharing personal info like when her ex was annoying her by texting from different numbers, and a lot more personal details about her past ( which according to her she never told others before ) she seems innocent and all. At times I have noticed she is little off the hook like won’t reply much during the day but that’s understandable because she is travelling . So in all I don’t feel she is showing any big issue. But there is a major issue going on with me. I am not able to get why is this , like I get very anxious when I don’t hear back from her , I even keep checking her online status and feel real pain if she come online and don’t respond , I even assumed she went for a trip to meet other guy ( no evidence ) . I almost couldn’t function if I sense slight change in responses . Even I asked her directly hey you are online , and she said yeah talking to my friends. I know this is not healthy , I know this will be a disaster and no one should be like that , like I am sure my rational brain knows that this is ridiculous but my heart and my emotions are liek totally in her hands ( I am not sure she even know it ) . Can someone give me some tips on how can I push this back . Some days I get worry so much ( usually when I feel later response etc ) that I think of just ending it all . I even know this is not yet a relationship but then I don’t get what’s going on with me.

tl;dr I am feeling highly anxious about the girl I started talking a month ago. I don’t see any obvious signs of manipulation but not sure what’s up with me.